Method and apparatus for controlling force feedback interface systems utilizing a host computer

ABSTRACT

A method and apparatus for controlling and providing force feedback using an interface device manipulated by a user. A microprocessor is provided local to the interface device and reads sensor data from sensors that describes the position and/or other information about a user object moved by the user, such as a joystick. The microprocessor controls actuators to provide forces on the user object and provides the sensor data to a host computer that is coupled to the interface device. The host computer sends high level host commands to the local microprocessor, and the microprocessor independently implements a local reflex process based on the high level command to provide force values to the actuators using sensor data and other parameters. A provided host command protocol includes a variety of different types of host commands and associated command parameters. By providing a relatively small set of high level host commands and parameters which are translated into a panoply of forces, the protocol further shifts the computational burden from the host computer to the local microprocessor and allows a software developer to easily create force feedback applications.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of co-pending parentpatent application Ser. No. 08/461,170, originally filed Jul. 16, 1993,on behalf of Louis B. Rosenberg et al., entitled, “Three-DimensionalMechanical Mouse,” and co-pending parent patent application Ser. No.08/534,791, filed Sep. 27, 1995, on behalf of Louis B. Rosenberg,entitled, “Method and Apparatus for Controlling Human-Computer InterfaceSystems Providing Force Feedback,” both assigned to the assignee of thispresent application, and both of which are incorporated by referenceherein.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to interface devicesbetween humans and computers, and more particularly to computerinterface devices that provide force feedback to the user.

[0003] Computer systems are used extensively in many differentindustries to implement computer controlled simulations, games, andother application programs. More particularly, these types of games andsimulations are very popular with the mass market of home consumers. Acomputer system typically displays a visual environment to a user on adisplay screen or other visual output device. Users can interact withthe displayed environment to play a game, experience a simulation or“virtual reality” environment, or otherwise influence events or imagesdepicted on the screen. Such user interaction can be implemented throughthe use of a human-computer interface device, such as a joystick,“joypad” button controller, mouse, trackball, stylus and tablet, or thelike, that is connected to the computer system controlling the displayedenvironment. The computer updates the simulation or game in response tothe user's manipulation of an object such as a joystick handle or mouse,and provides feedback to the user utilizing the display screen and,typically, audio speakers.

[0004] In some interface devices, tactile (“haptic”) feedback is alsoprovided to the user, more generally known as “force feedback.” Thesetypes of interface devices can provide physical sensations to the usermanipulating the object of the interface device. Typically, motors orother actuators are coupled to the object and are connected to thecontrolling computer system. The computer system can provide forces onthe object in conjunction with simulation/game events by sending controlsignals to the actuators. The computer system can thus convey physicalsensations to the user in conjunction with other supplied feedback asthe user is grasping or contacting the object of the interface device.Force feedback interface devices can thus provide a whole new modalityfor human-computer interaction.

[0005] Force feedback input/output (I/O) devices of the prior art haveconcentrated on providing maximum haptic fidelity, i.e., the realism ofthe tactile feedback was desired to be optimized. This is because mostof the force feedback devices have been targeted at the specific needsof highly industrial applications, and not a mass consumer market. Toattain such realism, mass market design concerns such as low size andweight, low complexity, programming compatibility, low cost, and safetyhave been sacrificed in the prior art. As a result, typical forcefeedback interface devices include complex robotic mechanisms whichrequire precision components and expensive actuators.

[0006] An important concern for a force feedback interface device iscommunication bandwidth between the controlling computer and theinterface device. To provide realistic force feedback, the complexdevices of the prior art typically use high speed communicationelectronics that allow the controlling computer to quickly update forcefeedback signals to the interface device. The more quickly thecontrolling computer can send and receive signals to and from theinterface device, the more accurately and realistically the desiredforces can be applied on the interface object. In addition, using a highbandwidth communication interface, force feedback can be accurately.coordinated with other supplied feedback, such as images on the videoscreen, and with user inputs such as movement of the object, activatedbuttons, etc. For example, a user can grasp and move a force feedbackjoystick in a simulation to control an image of a car to drive over avirtual bumpy surface displayed on a screen. The controlling computershould provide control signals to the actuators of the joystick quicklyenough so that the surface feels as realistically bumpy as the designerof the simulation intended. If the control signals are too slow, arealistic feeling of bumpiness is more difficult to provide. Also, thecontrolling computer needs a high bandwidth communication interface toaccurately coordinate the supplied forces with the visual feedback onthe screen, such as the moment on the screen when the car first contactsthe bumpy surface. This high speed is likewise needed to accuratelycoordinate supplied forces with any input from the user, for example, tosteer the car in particular directions.

[0007] A problem is evident when prior art force feedback interfacedevices are provided to the mass consumer market. Most home computershave a built-in standard serial communication interfaces, such as anRS-232 or RS-422 interface, that may conveniently be used to connectperipherals like a force feedback interface device to the host computer.In addition, manufacturers prefer to provide peripheral devices that usethese serial interfaces, since no additional hardware, such as interfacecards, needs to be provided with such peripherals. The manufacturingcost of the peripheral device can thus be significantly reduced.However, these standard serial communication interfaces are typicallyquite slow (i.e. have low bandwidth) compared to other communicatoninterfaces. Realistic and accurate force feedback thus becomes difficultto provide by a controlling computer system to a prior art interfacedevice connected through such a serial interface. For example, U.S. Pat.No. 5,184,319, by J. Kramer, describes a force feedback device thatapplies forces to a user's body parts. However, the Kramer device istypical of the prior art in that the host computer directly controls theactuators and directly receives the sensor data from the interfaceapparatus. Such a device is not suitable for a low bandwidthcommunication interface to achieve realistic force feedback.

[0008] Another problem with using prior art force feedback interfacedevices in the mass consumer market is the wide variety of computerplatforms and processing speeds that are used on different computers andon the same computer at different times. The force sensations providedto a user by a force feedback interface device may feel different to auser on different computer platforms or microprocessors, since thesedifferent computers run at different speeds. For example, the forcefeedback controlled by a 100 MHz computer may be much different from theforce feedback controlled by a 60 MHz computer due to the differentrates of processing control signals, even though these forces areintended to feel the same. In addition, the effective processing speedof one microprocessor can vary over time to provide inconsistent forcesover multiple user sessions. For example, multitasking can vary or delaya microprocessor's management of force feedback control signalsdepending on other programs that are running on the microprocessor.

[0009] In addition, there is no standardized language or communicationprotocol for communicating with force feedback devices. A softwaredeveloper that wishes to provide force feedback to an interface in asoftware application must currently set up his or her own specializedcommands and/or communications protocols and must implement the forcefeedback controlling instructions at a low level. This requiresunnecessary time and expense in the development of software applicationsthat include features directed toward force feedback interfaces.

[0010] Therefore, a more realistic, cost effective, and standardizedalternative to force feedback interfaces and force feedback controlparadigms is desired for certain applications.

SUMMARY OF THE INVENTION

[0011] The present invention is directed to controlling and providingforce feedback to a user operating a human/computer interface device.The interface device is connected to a controlling host computer andincludes a separate microprocessor local to the interface device. Thelocal microprocessor receives high-level host commands and implementsindependent reflex processes.

[0012] More particularly, a system and method of the present inventionfor controlling an interface apparatus manipulated by a user includes ahost computer system for receiving an input control signal and forproviding a host command. The host computer updates a host applicationprocess, such as a simulation or video game, in response to the inputcontrol signal. A microprocessor local to the interface apparatus andseparate from the host computer receives the host command and provides aprocessor output control signal. An actuator receives the processoroutput control signal and provides a force along a degree of freedom toa user-manipulated object, such as a joystick, in accordance with theprocessor output control signal. A sensor detects motion of the userobject along the degree of freedom and outputs the input control signalincluding information representative of the position and motion of theobject. Preferably, the sensor outputs the input control signal to thelocal microprocessor, which outputs the input control signal to the hostcomputer. The user object is preferably grasped and moved by the user,and can include such articles as a joystick, mouse, simulated medicalinstrument, stylus, or other object. The user object can preferably bemoved in one or more degrees of freedom using, for example, a gimbal orslotted yoke mechanism, where an actuator and sensor can be provided foreach degree of freedom.

[0013] The application process updated by the host computer systempreferably includes application software that can be simulationsoftware, game software, scientific software, etc. The host computersystem displays images on a visual output device such as a displayscreen and synchronizes the images and visual events with the positionand motion of the user object as well as forces applied to the object.The present invention can use a standard serial interface included onmany computers to interface the host computer system with the localmicroprocessor. A clock is preferably coupled to the host computersystem and/or the local processor which can be accessed for timing datato help determine the force output by the actuator.

[0014] In the preferred “reflex” embodiment, the host computer receivesthe sensor information in a supervisory mode and outputs a high levelhost command to the microprocessor whenever a force is required to beapplied to the user object or changed. In accordance with the high levelhost command, the microprocessor reads sensor and timing data andoutputs force values to the actuator according to a reflex process thatis selected. The reflex process can include using force equations,reading force profiles of predetermined force values from a storagedevice, or other steps, and may be dependent on sensor data, timingdata, host command data, or other data. The processor thus implements areflex to control forces independently of the host computer until thehost computer changes the type of force applied to the user object.

[0015] The invention also provides a paradigm for force commands betweenthe host computer and the local microprocessor. The high level hostcommands provided by the host computer can be rate control and/orposition control commands, and may include information in the form ofcommand parameters. By providing a relatively small set of commands andcommand parameters which are translated into a panoply of forces, theparadigm further shifts the computational burden from the host computerto the local microprocessor. Host commands may include commands toprovide forces on the user object such as restoring forces, vibrationforces, texture forces, a barrier forces, attractive/repulsive forcefields, damping forces, groove forces, and a paddle-ball force. Typicalcommand parameters include a magnitude parameter, a duration parameter,a direction parameter, a style parameter, and a button parameter tocontrol the force output by the actuator. This provides a high level,standard force feedback command protocol for the efficient use bydevelopers of force feedback software to be implemented on the hostcomputer system.

[0016] A preferred implementation of the functionality of the localmicroprocessor is also provided. A command process receives a hostcommand from the host computer and processes the host command and anycommand parameters included in the host command. Force parameters arederived from the host command and the command parameter and are storedin memory. Preferably, every host command has a set of force parametersassociated with it to be updated when the appropriate host command isreceived. A status update process reads sensor data from the sensorsdescribing a motion of the user object. The status update process canalso compute velocity, acceleration, or other time-related values ifappropriate. A force output process computes a force value using areflex process selected in accordance with the force parameters and thesensor data. In some instances, the force value may depend on the valuesof the force parameters and sensor data. The force output processoutputs a force on the user object by sending the computed force valueto the actuators. In addition, a reporting process reports the sensordata to the host computer system when appropriate. Preferably, aplurality of host commands can be in effect simultaneously, where aforce value is summed from a reflex process corresponding to each suchhost command in effect. Also, parameter page(s) of sets of parameterscan conveniently be stored in memory to allow different forceenvironments to be selected.

[0017] The control system and method of the present inventionadvantageously includes a separate processor local to the interfacedevice that is separate from the host computer system. The localprocessor can read and process sensor signals as well as output forcecommand signals independently of the host computer, thus savingsignificant processing time on the host computer. In addition, the useof the local processor to handle low-level force feedback commandsallows more realistic and accurate force feedback to be provided to anobject manipulated by a user when using a serial or other relativelylow-bandwidth communication interface between the host and the interfacedevice, since such low level force signals do not have to be transmittedover the communication interface. The use of specific, high level hostcommands to command a variety of types of forces allows force feedbackhost applications to be easily created. These improvements allow acomputer system to provide accurate and realistic force feedback over alow-cost, low bandwidth communication interface and is thus ideal forthe mass market of home computer systems.

[0018] These and other advantages of the present invention will becomeapparent to those skilled in the art upon a reading of the followingspecification of the invention and a study of the several figures of thedrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a block diagram of a control system in accordance withthe present invention for controlling a force feedback interface devicefrom a host computer;

[0020]FIG. 2 is a schematic diagram of an actuator interface forproviding control signals to an active actuator for the presentinvention;

[0021]FIG. 3 is a schematic diagram of an actuator interface forproviding control signals to a passive actuator for the presentinvention;

[0022]FIG. 4 is a flow diagram illustrating a first embodiment of amethod of the present invention for controlling a force feedbackinterface device;

[0023]FIG. 5 is a flow diagram illustrating a second embodiment of amethod of the present invention for controlling a force feedbackinterface device;

[0024]FIG. 6 is a schematic diagram of a closed loop five bar linkagemechanism for providing two degrees of freedom to the user object of theinterface device;

[0025]FIG. 7 is a perspective view of a preferred embodiment of thelinkage mechanism shown in FIG. 6;

[0026]FIG. 8 is a perspective view of a slotted yoke joystick embodimentof a mechanical interface for the user object;

[0027]FIG. 9 is a table summarizing rate control commands of the presentinvention;

[0028]FIGS. 10a-c are diagrammatic representations of restoring forceprofiles;

[0029]FIGS. 11a-c are diagrammatic representations of restoring springforce profiles;

[0030]FIG. 12 is a diagrammatic representation of a vector force;

[0031]FIGS. 13a-b are diagrammatic representations of vibration forceprofiles;

[0032]FIG. 14 is a table summarizing position control commands of thepresent invention;

[0033]FIG. 15 is a diagrammatic representation of a groove forceprofile;

[0034]FIG. 16 is a diagrammatic representation of a barrier forceprofile;

[0035]FIGS. 17a-17 i are diagrammatic illustrations of a paddle and ballinteraction controlled by a paddle command of the present invention;

[0036]FIG. 18 is a block diagram illustrating an implementation of thelocal microprocessor of the present invention for controlling a forcefeedback interface device with host commands containing forceparameters;

[0037]FIG. 19 is a flow diagram illustrating a host communicationbackground process of FIG. 18;

[0038]FIG. 20 is a flow diagram illustrating a command process of FIG.18;

[0039]FIG. 21 is a flow diagram illustrating a reporting process of FIG.18;

[0040]FIG. 22 is a flow diagram illustrating force algorithm computationand actuator control process of FIG. 18; and

[0041]FIG. 23 is a diagrammatic representation of force parameters and asequence of force commands as used in the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0042]FIG. 1 is a block diagram illustrating a generic control system 10of the present invention for an interface device controlled by a hostcomputer system. Control system 10 includes a host computer system 12and an interface device 14.

[0043] Host computer system 12 is preferably a personal computer, suchas an IBM-compatible or Macintosh personal computer, or a workstation,such as a SUN or Silicon Graphics workstation. For example, the hostcomputer system can a personal computer which operates under the MS-DOSor Windows operating systems in conformance with an IBM PC AT standard.Alternatively, host computer system 12 can be one of a variety of homevideo game systems commonly connected to a television set, such assystems available from Nintendo, Sega, or Sony. In other embodiments,home computer system 12 can be a “set top box” which can be used, forexample, to provide interactive television functions to users.

[0044] In the described embodiment, host computer system 12 implements ahost application program with which a user 22 is interacting viaperipherals and interface device 14. For example, the host applicationprogram can be a video game, medical simulation, scientific analysisprogram, or even an operating system or other application program thatutilizes force feedback. Typically, the host application provides imagesto be displayed on a display output device, as described below, and/orother feedback, such as auditory signals.

[0045] Host computer system 12 preferably includes a host microprocessor16, random access memory (RAM) 17, read-only memory (ROM) 19,input/output (I/O) electronics 21, a clock 18, a display screen 20, andan audio output device 21. Host microprocessor 16 can include a varietyof available microprocessors from Intel, Motorola, or othermanufacturers. Microprocessor 16 can be single microprocessor chip, orcan include multiple primary and/or co-processors. Microprocessorpreferably retrieves and stores instructions and other necessary datafrom RAM 17 and ROM 19, as is well known to those skilled in the art. Inthe described embodiment, host computer system 12 can receive sensordata or a sensor signal via a bus 24 from sensors of interface device 14and other information. Microprocessor 16 can receive data from bus 24using I/O electronics 21, and can use I/O electronics to control otherperipheral devices. Host computer system 12 can also output a “forcecommand” to interface device 14 via bus 24 to cause force feedback forthe interface device.

[0046] Clock 18 is a standard clock crystal or equivalent component usedby host computer system 12 to provide timing to electrical signals usedby microprocessor 16 and other components of the computer system. Clock18 is accessed by host computer system 12 in the control process of thepresent invention, as described subsequently.

[0047] Display screen 20 is coupled to host microprocessor 16 bysuitable display drivers and can be used to display images generated byhost computer system 12 or other computer systems. Display screen 20 canbe a standard display screen or CRT, 3-D goggles, or any other visualinterface. In a described embodiment, display screen 20 displays imagesof a simulation or game environment. In other embodiments, other imagescan be displayed. For example, images describing a point of view from afirst-person perspective can be displayed, as in a virtual realitysimulation or game. Or, images describing a third-person perspective ofobjects, backgrounds, etc. can be displayed. A user 22 of the hostcomputer 12 and interface device 14 can receive visual feedback byviewing display screen 20.

[0048] Herein, computer 12 may be referred as displaying computer“objects” or “entities”. These computer objects are not physicalobjects, but is a logical software unit collections of data and/orprocedures that may be displayed as images by computer 12 on displayscreen 20, as is well known to those skilled in the art. For example, acursor or a third-person view of a car might be consideredplayer-controlled computer objects that can be moved across the screen.A displayed, simulated cockpit of an aircraft might also be consideredan “object”, or the simulated aircraft can be considered a computercontrolled “entity”.

[0049] Audio output device 21, such as speakers, is preferably coupledto host microprocessor 16 via amplifiers, filters, and other circuitrywell known to those skilled in the art. Host processor 16 outputssignals to speakers 21 to provide sound output to user 22 when an “audioevent” occurs during the implementation of the host application program.Other types of peripherals can also be coupled to host processor 16,such as storage devices (hard disk drive, CD ROM drive, floppy diskdrive, etc.), printers, and other input and output devices.

[0050] An interface device 14 is coupled to host computer system 12 by abi-directional bus 24. The bi-directional bus sends signals in eitherdirection between host computer system 12 and the interface device.Herein, the term “bus” is intended to generically refer to an interfacesuch as between host computer 12 and microprocessor 26 which typicallyincludes one or more connecting wires or other connections and that canbe implemented in a variety of ways, as described below. In thepreferred embodiment, bus 24 is a serial interface bus providing dataaccording to a serial communication protocol. An interface port of hostcomputer system 12, such as an RS232 serial interface port, connects bus24 to host computer system 12. Other standard serial communicationprotocols can also be used in the serial interface and bus 24, such asRS-422, Universal Serial Bus (USB), MIDI, or other protocols well knownto those skilled in the art.

[0051] For example, the USB standard provides a relatively high speedserial interface that can provide force feedback signals in the presentinvention with a high degree of realism. USB can also source more powerto drive peripheral devices. Since each device that accesses the USB isassigned a unique USB address by the host computer, this allows multipledevices to share the same bus. In addition, the USB standard includestiming data that is encoded along with differential data. The USB hasseveral useful features for the present invention, as describedthroughout this specification.

[0052] An advantage of the present invention is that low-bandwidthserial communication signals can be used to interface with interfacedevice 14, thus allowing a standard built-in serial interface of manycomputers to be used directly. Alternatively, a parallel port of hostcomputer system 12 can be coupled to a parallel bus 24 and communicatewith interface device using a parallel protocol, such as SCSI or PCParallel Printer Bus. In a different embodiment, bus 24 can be connecteddirectly to a data bus of host computer system 12 using, for example, aplug-in card and slot or other access of computer system 12. Forexample, on an IBM AT compatible computer, the interface card can beimplemented as an ISA, EISA, VESA local bus, PCI, or other well-knownstandard interface card which plugs into the motherboard of the computerand provides input and output ports connected to the main data bus ofthe computer.

[0053] In another embodiment, an additional bus 25 can be included tocommunicate between host computer system 12 and interface device 14.Since the speed requirement for communication signals is relatively highfor outputting force feedback signals, the single serial interface usedwith bus 24 may not provide signals to and from the interface device ata high enough rate to achieve realistic force feedback. In such anembodiment, bus 24 can be coupled to the standard serial port of hostcomputer 12, while an additional bus 25 can be coupled to a second portof the host computer system. For example, many computer systems includea “game port” in addition to a serial RS-232 port to connect a joystickor similar game controller to the computer. The two buses 24 and 25 canbe used simultaneously to provide a increased data bandwidth. Forexample, microprocessor 26 can send sensor signals to host computer 12via a unidirectional bus 25 and a game port, while host computer 12 canoutput force feedback signals from a serial port to microprocessor 26via a uni-directional bus 24. Other combinations of data flowconfigurations can be implemented in other embodiments.

[0054] Interface device 14 includes a local microprocessor 26, sensors28, actuators 30, a user object 34, optional sensor interface 36, anoptional actuator interface 38, and other optional input devices 39.Interface device 14 may also include additional electronic componentsfor communicating via standard protocols on bus 24. In the preferredembodiment, multiple interface devices 14 can be coupled to a singlehost computer system 12 through bus 24 (or multiple buses 24) so thatmultiple users can simultaneously interface with the host applicationprogram (in a multi-player game or simulation, for example). Inaddition, multiple players can interact in the host application programwith multiple interface devices 14 using networked host computers 12, asis well known to those skilled in the art.

[0055] Local microprocessor 26 is coupled to bus 24 and is preferablyincluded within the housing of interface device 14 to allow quickcommunication with other components of the interface device. Processor26 is considered “local” to interface device 14, where “local” hereinrefers to processor 26 being a separate microprocessor from anyprocessors in host computer system 12. “Local” also preferably refers toprocessor 26 being dedicated to force feedback and sensor I/O ofinterface device 14, and being closely coupled to sensors 28 andactuators 30, such as within the housing for interface device or in ahousing coupled closely to interface device 14. Microprocessor 26 can beprovided with software instructions to wait for commands or requestsfrom computer host 16, decode the command or request, and handle/controlinput and output signals according to the command or request. Inaddition, processor 26 preferably operates independently of hostcomputer 16 by reading sensor signals and calculating appropriate forcesfrom those sensor signals, time signals, and a reflex process (alsoreferred to as a “subroutine” or “force sensation process” herein)selected in accordance with a host command. Suitable microprocessors foruse as local microprocessor 26 include the MC68HC711E9 by Motorola andthe PIC16C74 by Microchip, for example. Microprocessor 26 can includeone microprocessor chip, or multiple processors and/or co-processorchips. In other embodiments, microprocessor 26 can includes a digitalsignal processor (DSP) chip. Local memory 27, such as RAM and/or ROM, ispreferably coupled to microprocessor 26 in interface device 14 to storeinstructions for microprocessor 26 and store temporary and other data.Microprocessor 26 can receive signals from sensors 28 and providesignals to actuators 30 of the interface device 14 in accordance withinstructions provided by host computer 12 over bus 24.

[0056] In addition, a local clock 29 can be coupled to themicroprocessor 26 to provide timing data, similar to system clock 18 ofhost computer 12; the timing data might be required, for example, tocompute forces output by actuators 30 (e.g., forces dependent oncalculated velocities or other time dependent factors). In alternateembodiments using the USB communication interface, timing data formicroprocessor 26 can be retrieved from USB signal. The USB has a clocksignal encoded with the data stream which can be used. Alternatively,the Isochronous (stream) mode of USB can be used to derive timinginformation from the standard data transfer rate. The USB also has aSample Clock, Bus Clock, and Service Clock that also may be used.

[0057] For example, in one embodiment, host computer 12 can providelow-level force commands over bus 24, which microprocessor 26 directlyprovides to actuators 30. This embodiment is described in greater detailwith respect to FIG. 4. In a different embodiment, host computer system12 can provide high level supervisory commands to microprocessor 26 overbus 24, and microprocessor 26 manages low level force control (“reflex”)loops to sensors 28 and actuators 30 in accordance with the high levelcommands. This embodiment is described in greater detail with respect toFIG. 5.

[0058] Microprocessor 26 preferably also has access to an electricallyerasable programmable ROM (EEPROM) or other memory storage device 27 forstoring calibration parameters. The calibration parameters cancompensate for slight manufacturing variations in different physicalproperties of the components of different interface devices made fromthe same manufacturing process, such as physical dimensions. Thecalibration parameters can be determined and stored by the manufacturerbefore the interface device 14 is sold, or optionally, the parameterscan be determined by a user of the interface device. The calibrationparameters are used by processor 26 to modify the input sensor signalsand/or output force values to actuators 30 to provide approximately thesame range of forces on object 34 in a large number of manufacturedinterface devices 14. The implementation of calibration parameters iswell-known to those skilled in the art.

[0059] Microprocessor 26 can also receive commands from any other inputdevices included on interface apparatus 14 and provides appropriatesignals to host computer 12 to indicate that the input information hasbeen received and any information included in the input information. Forexample, buttons, switches, dials, or other input controls on interfacedevice 14 or user object 34 can provide signals to microprocessor 26.

[0060] In the preferred embodiment, sensors 28, actuators 30, andmicroprocessor 26, and other related electronic components are includedin a housing for interface device 14, to which user object 34 isdirectly or indirectly coupled. Alternatively, microprocessor 26 and/orother electronic components of interface device 14 can be provided in aseparate housing from user object 34, sensors 28, and actuators 30.Also, additional mechanical structures may be included in interfacedevice 14 to provide object 34 with desired degrees of freedom. Someembodiments of such mechanisms are described with reference to FIGS.7-12.

[0061] Sensors 28 sense the position, motion, and/or othercharacteristics of a user object 34 of the interface device 14 along oneor more degrees of freedom and provide signals to microprocessor 26including information representative of those characteristics. Examplesof embodiments of user objects and movement within provided degrees offreedom are described subsequently with respect to FIGS. 7 and 8.Typically, a sensor 28 is provided for each degree of freedom alongwhich object 34 can be moved. Alternatively, a single compound sensorcan be used to sense position or movement in multiple degrees offreedom. An example of sensors suitable for several embodimentsdescribed herein are digital optical encoders, which sense the change inposition of an object about a rotational axis and provide digitalsignals indicative of the change in position. The encoder, for example,responds to a shaft's rotation by producing two phase-related signals inthe rotary degree of freedom. Linear optical encoders similarly sensethe change in position of object 34 along a linear degree of freedom,and can produces the two phase-related signals in response to movementof a linear shaft in the linear degree of freedom. Either relative orabsolute sensors can be used. For example, relative sensors only providerelative angle information, and thus usually require some form ofcalibration step which provide a reference position for the relativeangle information. The sensors described herein are primarily relativesensors. In consequence, there is an implied calibration step aftersystem power-up wherein a sensor's shaft is placed in a known positionwithin interface device and a calibration signal is provided to thesystem to provide the reference position mentioned above. All anglesprovided by the sensors are thereafter relative to that referenceposition. Alternatively, a known index pulse can be provided in therelative sensor which can provide a reference position. Such calibrationmethods are well known to those skilled in the art and, therefore, willnot be discussed in any great detail herein. A suitable optical encoderis the “Softpot” from U.S. Digital of Vancouver, Wash.

[0062] Sensors 28 provide an electrical signal to an optional sensorinterface 36, which can be used to convert sensor signals to signalsthat can be interpreted by the microprocessor 26 and/or host computersystem 12. For example, sensor interface 36 receives the twophase-related signals from a sensor 28 and converts the two signals intoanother pair of clock signals, which drive a bi-directional binarycounter. The output of the binary counter is received by microprocessor26 as a binary number representing the angular position of the encodedshaft. Such circuits, or equivalent circuits, are well known to thoseskilled in the art; for example, the Quadrature Chip LS7166 from HewlettPackard, California performs the functions described above. Each sensor28 can be provided with its own sensor interface, or one sensorinterface may handle data from multiple sensors. For example, theelectronic interface described in parent patent application Ser. No.08/092,974 describes a sensor interface including a separate processingchip dedicated to each sensor that provides input data. Alternately,microprocessor 26 can perform these interface functions without the needfor a separate sensor interface 36. The position value signals can beused by microprocessor 26 and are also sent to host computer system 12which updates the host application program and sends force controlsignals as appropriate. For example, if the user moves a steering wheelobject 34, the computer system 12 receives position and/or other signalsindicating this movement and can move a displayed point of view of theuser as if looking out a vehicle and turning the vehicle. Otherinterface mechanisms can also be used to provide an appropriate signalto host computer system 12. In alternate embodiments, sensor signalsfrom sensors 28 can be provided directly to host computer system 12,bypassing microprocessor 26. Also, sensor interface 36 can be includedwithin host computer system 12, such as on an interface board or card.

[0063] Alternatively, an analog sensor can be used instead of digitalsensor for all or some of the sensors 28. For example, a strain gaugecan be connected to measure forces on object 34 rather than positions ofthe object. Also, velocity sensors and/or accelerometers can be used todirectly measure velocities and accelerations on object 34. Analogsensors can provide an analog signal representative of theposition/velocity/acceleration of the user object in a particular degreeof freedom. An analog to digital converter (ADC) can convert the analogsignal to a digital signal that is received and interpreted bymicroprocessor 26 and/or host computer system 12, as is well known tothose skilled in the art. The resolution of the detected motion ofobject 34 would be limited by the resolution of the ADC. However, noisecan sometimes mask small movements of object 34 from an analog sensor,which can potentially mask the play that is important to someembodiments of the present invention (described subsequently).

[0064] Other types of interface circuitry 36 can also be used. Forexample, an electronic interface is described in U.S. patent applicationSer. No. 08/092,974, entitled “3-D Mechanical Mouse”, previouslyincorporated herein. The interface allows the position of the mouse orstylus to be tracked and provides force feedback to the stylus usingsensors and actuators. Sensor interface 36 can include angle determiningchips to pre-process angle signals reads from sensors 28 before sendingthem to the microprocessor 26. For example, a data bus plus chip-enablelines allow any of the angle determining chips to communicate with themicroprocessor. A configuration without angle-determining chips is mostapplicable in an embodiment having absolute sensors, which have outputsignals directly indicating the angles without any further processing,thereby requiring less computation for the microprocessor 26 and thuslittle if any pre-processing. If the sensors 28 are relative sensors,which indicate only the change in an angle and which require furtherprocessing for complete determination of the angle, thenangle-determining chips are more appropriate.

[0065] Actuators 30 transmit forces to user object 34 of the interfacedevice 14 in one or more directions along one or more degrees of freedomin response to signals received from microprocessor 26. Typically, anactuator 30 is provided for each degree of freedom along which forcesare desired to be transmitted. Actuators 30 can include two types:active actuators and passive actuators.

[0066] Active actuators include linear current control motors, steppermotors, pneumatic/hydraulic active actuators, and other types ofactuators that transmit a force to move an object. For example, activeactuators can drive a rotational shaft about an axis in a rotary degreeof freedom, or drive a linear shaft along a linear degree of freedom.Active transducers of the present invention are preferablybi-directional, meaning they can selectively transmit force along eitherdirection of a degree of freedom. For example, DC servo motors canreceive force control signals to control the direction and torque (forceoutput) that is produced on a shaft. The motors may also include brakeswhich allow the rotation of the shaft to be halted in a short span oftime. Other types of active motors can also be used, such as a steppermotor controlled with pulse width modulation of an applied voltage,pneumatic/hydraulic actuators, a torquer (motor with limited angularrange), or a voice coil actuator, which are well known to those skilledin the art.

[0067] Passive actuators can also be used for actuators 30. Magneticparticle brakes, friction brakes, or pneumatic/hydraulic passiveactuators can be used in addition to or instead of a motor to generate adamping resistance or friction in a degree of motion. An alternatepreferred embodiment only including passive actuators may not be asrealistic as an embodiment including motors; however, the passiveactuators are typically safer for a user since the user does not have tofight generated forces. Passive actuators typically can only providebi-directional resistance to a degree of motion. A suitable magneticparticle brake for interface device 14 is available from Force Limited,Inc. of Santa Monica, Calif.

[0068] In alternate embodiments, all or some of sensors 28 and actuators30 can be included together as a sensor/actuator pair transducer. Asuitable transducer for the present invention including both an opticalencoder and current controlled motor is a 20 W basket wound servo motormanufactured by Maxon.

[0069] Actuator interface 38 can be optionally connected betweenactuators 30 and microprocessor 26. Interface 38 converts signals frommicroprocessor 26 into signals appropriate to drive actuators 30.Interface 38 can include power amplifiers, switches, digital to analogcontrollers (DACs), and other components. An example of an actuatorinterface for active actuators is described with reference to FIG. 2. Anexample of an actuator interface for passive actuators is described withreference to FIG. 3. In alternate embodiments, interface 38 circuitrycan be provided within microprocessor 26 or in actuators 30.

[0070] Other input devices 39 can optionally be included in interfacedevice 14 and send input signals to microprocessor 26. Such inputdevices can include buttons, dials, switches, or other mechanisms. Forexample, in embodiments where user object 34 is a joystick, other inputdevices can include one or more buttons provided, for example, on thejoystick handle or base and used to supplement the input from the userto a game or simulation. The operation of such input devices is wellknown to those skilled in the art.

[0071] Power supply 40 can optionally be coupled to actuator interface38 and/or actuators 30 to provide electrical power. Active actuatorstypically require a separate power source to be driven. Power supply 40can be included within the housing of interface device 14, or can beprovided as a separate component, for example, connected by anelectrical power cord.

[0072] Alternatively, if the USB or a similar communication protocol isused, interface device 14 can draw power from the USB and thus have noneed for power supply 40. This embodiment is most applicable to a device14 having passive actuators 30, since passive actuators require littlepower to operate. Active actuators tend to require more power than canbe drawn from USB, but this restriction can be overcome in a number ofways. One way is to configure interface 14 to appear as more than oneperipheral to host computer 12; for example, each provided degree offreedom of user object 34 can be configured as a different peripheraland receive its own allocation of power. This would allow host 12 toallocate more power to interface device 14. Alternatively, power fromthe USB can be stored and regulated by interface device 14 and thus usedwhen needed to drive actuators 30. For example, power can be stored overtime and then immediately dissipated to provide a jolt force to the userobject 34. A capacitor circuit, for example, can store the energy anddissipate the energy when enough power has been stored. Microprocessormay have to regulate the output of forces to assure that time is allowedfor power to be stored. This power storage embodiment can also be usedin non-USB embodiments of interface device 14 to allow a smaller powersupply 40 to be used.

[0073] Safety switch 41 is preferably included in interface device toprovide a mechanism to allow a user to override and deactivate actuators30, or require a user to activate actuators 30, for safety reasons.Certain types of actuators, especially active actuators such as motors,can pose a safety issue for the user if the actuators unexpectedly moveuser object 34 against the user with a strong force. In addition, if afailure in the control system 10 occurs, the user may desire to quicklydeactivate the actuators to avoid any injury. To provide this option,safety switch 41 is coupled to actuators 30. In the preferredembodiment, the user must continually activate or close safety switch 41during operation of interface device 14 to activate the actuators 30.If, at any time, the safety switch is deactivated (opened), power frompower supply 40 is cut to actuators 30 (or the actuators are otherwisedeactivated) as long as the safety switch is deactivated. For example, apreferred embodiment of safety switch is an optical switch located onuser object 34 (such as a joystick) or on a convenient surface of ahousing enclosing interface device 14. When the user covers the opticalswitch with a hand or finger, the sensor of the switch is blocked fromsensing ambient light, and the switch is closed. The actuators 30 thuswill function as long as the user covers the switch. Other types ofsafety switches 41 can be provided in other embodiments. For example, anelectrostatic contact switch can be used to sense contact, a button ortrigger can be pressed, or a different type of sensor switch can beused.

[0074] User object 34 is preferably a device or article that may begrasped or otherwise contacted or controlled by a user and which iscoupled to interface device 14. By “grasp”, it is meant that users mayreleasably engage a grip portion of the object in some fashion, such asby hand, with their fingertips, or even orally in the case ofhandicapped persons. The user 22 can manipulate and move the objectalong provided degrees of freedom to interface with the host applicationprogram the user is viewing on display screen 20. Object 34 can be ajoystick, mouse, trackball, stylus, steering wheel, medical instrument(laparoscope, catheter, etc.), pool cue, hand grip, knob, button, orother article.

[0075]FIG. 2 is a schematic diagram illustrating an example of anactuator interface 38 for an active actuator 30 of interface device 14.In this example, actuator 30 is a linear current controlled servo motor.Actuator interface 38 includes a DAC circuit 44 and a power amplifiercircuit 46.

[0076] DAC circuit 44 is coupled to microprocessor 26 and preferablyreceives a digital signal representing a force value from themicroprocessor 26. DAC 48 is suitable for converting an input digitalsignal to an analog voltage that is output to power amplifier circuit46. A suitable DAC 48 is a parallel DAC, such as the DAC1220manufactured by National Semiconductor, which is designed to operatewith external generic op amp 50. Op amp 50, for example, outputs asignal from zero to −5 volts proportional to the binary number at itsinput. Op amp 52 is an inverting summing amplifier that converts theoutput voltage to a symmetrical bipolar range. Op amp 52 produces anoutput signal between −2.5 V and +2.5 V by inverting the output of opamp 50 and subtracting 2.5 volts from that output; this output signal issuitable for power amplification in amplification circuit 46. As anexample, R1=200 kW and R2=400 kW. Of course, DAC circuit 44 is intendedas one example of many possible circuits that can be used to convert adigital signal to a desired analog signal.

[0077] Power amplifier circuit 46 receives an analog low-power controlvoltage from DAC circuit 44 and amplifies the voltage to controlactuators 30. Actuator 30 can be a high-power, current-controlled servomotor 30. The input voltage controls a transconductance stage composedof amplifier 54 and several resistors. The transconductance stageproduces an output current proportional to the input voltage to drivemotor 30 while drawing very little current from the input voltagesource. The second amplifier stage, including amplifier 56, resistors,and a capacitor C, provides additional current capacity by enhancing thevoltage swing of the second terminal 57 of motor 30. As example valuesfor power amplifier circuit 46, R=10 kW, R2=500 W, R3=9.75 kW, and R4=1W. Of course, circuit 46 is intended as one example of many possiblecircuits that can be used to amplify voltages to drive active actuators30.

[0078]FIG. 3 is a schematic diagram illustrating an example of anactuator interface 38′ that can be used in conjunction with passiveactuators. Interface 38′ is suitable for use with passive actuators(dampers) that are controlled with an analog voltage, such as magneticparticle brakes or a variable solenoid used with the fluid controlledpassive dampers of parent application Ser. No. 08/489,068. Interface 38′includes a DAC circuit 44, amplifier 60, transistor 62, and voltageprotector 64. DAC circuit 44 is coupled to microprocessor 26 andreceives a digital signal from the computer system representing aresistive force value to be applied to user object 34. DAC circuit 44converts the digital signal voltages to analog voltages which are thenoutput to amplifier 60. A suitable DAC is the MAX530ACNG manufactured byMaxim, or DAC circuit 44 as described above with reference to FIG. 2.Amplifier 60 receives the analog voltage from DAC 44 on a positiveterminal and scales the voltage signal to a range usable by actuator 30.Amplifier 60 can be implemented as an operational amplifier or the like.Transistor 62 is coupled to the output of amplifier 60 and preferablyoperates as an amplifier to provide increased output current to actuator30. Resistor R1 is coupled between amplifier 60 and the emitter oftransistor 62, and resistor R2 is coupled between amplifier 60 andground. For example, resistors R1 and R2 can have values of 180 k_ and120 k_, respectively, and provide the proper biasing in the circuit.Voltage protector 64 is coupled to the emitter of transistor 62 andprovides protection from voltage spikes when using inductive loads.Suitable passive actuators 30 for use with this circuitry includesvariable solenoids or magnetic particle brakes. A separate DAC andamplifier can be used for each actuator 30 implemented in the interfaceapparatus so the microprocessor 26 and/or host computer system 12 cancontrol each actuator separately for each provided degree of freedom.Interface 38′ is intended as one example of many possible circuits thatcan be used to interface a computer system to actuators.

[0079] In an alternate embodiment, an on/off signal might only beneeded, for example, for a solenoid driving an on/off valve of afluid-controlled actuator as described in co-pending patent applicationSer. No. 08/489,068 and below in FIG. 10. In such an embodiment, forexample, a transistor can be electrically coupled to microprocessor 26at its base terminal to operate as an electrical switch for controllingthe activation of a solenoid in the on/off actuator 30. A force signalsuch as a TTL logic signal can be sent to control the transistor toeither allow current to flow through the solenoid to activate it andallow free movement of object 43, or to allow no current to flow todeactivate the solenoid and provide resistance to movement.

[0080]FIG. 4 is a flow diagram illustrating a first embodiment of amethod 70 for controlling a force feedback interface device of thepresent invention. Method 70 is directed to a “host-controlled”embodiment, in which host computer system 12 provides direct, low-levelforce commands to microprocessor 26, and the microprocessor directlyprovides these force commands to actuators 30 to control forces outputby the actuators.

[0081] For example, the host controlled mode is suitable for embodimentsusing a USB communication interface. Data rates are sufficiently high toallow the host to communicate at 500 Hz or greater and provide realisticforce feedback to the user object 34. The USB Isochronous Data Transfermode of USB is suitable to provide the necessary high data rate.

[0082] The process begins at 72. In step 74, host computer system 12 andinterface device 14 are powered up, for example, by a user activatingpower switches. After step 74, the process 70 branches into two parallel(simultaneous) processes. One process is implemented on host computersystem 12, and the other process is implemented on local microprocessor26. These two processes branch out of step 74 in different directions toindicate this simultaneity.

[0083] In the host computer system process, step 76 is firstimplemented, in which an application program is processed or updated.This application can be a simulation, video game, scientific program, orother program. Images can be displayed for a user on output displayscreen 20 and other feedback can be presented, such as audio feedback.

[0084] Two branches exit step 76 to indicate that there are twoprocesses running simultaneously (multitasking) on host computer system12. In one process, step 78 is implemented, where sensor data isreceived by the host computer from local microprocessor 26. As detailedbelow in the microprocessor process, the local processor 26 continuallyreceives signals from sensors 28, processes the raw data, and sendsprocessed sensor data to host computer 12, Alternatively, localprocessor 26 sends raw data directly to host computer system 12. “Sensordata”, as referred to herein, can include position values, velocityvalues, and/or acceleration values derived from the sensors 28 whichdetect motion of object 34 in one or more degrees of freedom. Inaddition, any other data received from other input devices 39 can alsobe received by host computer system 12 as sensor data in step 78, suchas signals indicating a button on interface device 14 has been activatedby the user. Finally, the term “sensor data” also can include a historyof values, such as position values recorded previously and stored inorder to calculate a velocity.

[0085] After sensor data is read in step 78, the process returns to step76, where the host computer system 12 can update the application programin response to the user's manipulations of object 34 and any other userinput received in step 78 as well as determine if forces need to beapplied to object 34 in the parallel process. Step 78 is implemented ina continual loop of reading data from local processor 26.

[0086] The second branch from step 76 is concerned with the process ofthe host computer determining force commands to provide force feedbackto the user manipulating object 34. These commands are described hereinas “low-level” force commands, as distinguished from the “high-level” orsupervisory force commands described in the embodiment of FIG. 5. A lowlevel force command instructs an actuator to output a force of aparticular magnitude. For example, the low level command typicallyincludes a magnitude force value, e.g., equivalent signal(s) to instructthe actuator to apply a force of a desired magnitude value. Low levelforce commands may also designate a direction of force if an actuatorcan apply force in a selected direction, and/or other low-levelinformation as required by an actuator.

[0087] The second branch starts with step 80, in which the host computersystem checks if a change in the force applied to user object 34 isrequired. This can be determined by several types of criteria, the mostimportant of which are the sensor data read by the host computer in step78, timing data, and the implementation or “events” of the applicationprogram updated in step 76. The sensor data read in step 78 informs thehost computer 12 how the user is interacting with the applicationprogram. From the position of object 34 sensed over time, the hostcomputer system 12 can determine when forces should be applied to theobject. For example, if the host computer is implementing a video gameapplication, the position of a computer generated object within the gamemay determine if a change in force feedback is called for. If the useris controlling a simulated race car, the position of the user objectjoystick determines if the race car is moving into a wall and thus if acollision force should be generated on the joystick. In addition, thevelocity and/or acceleration of the user object can influence whether achange in force on the object is required. If the user is controlling atennis racket in a game, the velocity of a user object joystick in aparticular degree of freedom may determine if a tennis ball is hit andthis if an appropriate force should be applied to the joystick. Also,other input, such as a user activating buttons or other controls oninterface device 14, can change the forces required on object 34depending on how those controls have been programmed to affect theapplication program.

[0088] Other criteria for determining if a change in force is requiredincludes events in the application program. For example, a gameapplication program may (perhaps randomly) determine that another objectin the game is going to collide with an object controlled by the user,regardless of the position data of the user object 34. Forces shouldthus be applied to the user object dependent on this collision event tosimulate an impact. Forces can be required on the user object dependingon a combination of such an event and the sensor data read in step 78.Other parameters in the application program can determine if a change inforce to the user object is necessary, such as other input devices oruser interface devices connected to host computer system 12 andinputting data to the application program (other interface devices canbe directly connected, connected remotely through a network, etc.).

[0089] If no change in force is currently required in step 80, then theprocess returns to step 76 to update the host application and return tostep 80 to again check until such a change in force is required. Whensuch a change is required, step 82 is implemented, in which hostcomputer 12 determines appropriate low-level force commands to be sentto the actuators 30 of interface device 14, these force commands beingdependent on a selected force sensation process, sensor data, the hostapplication, and the clock 18.

[0090] The low-level force commands can be determined, in part, from aselected force sensation process. A “reflex process” or “force sensationprocess”, as referred to herein, is a set of instructions for providingforce commands dependent on other parameters, such as sensor data readin step 78 and timing data from clock 18. In the described embodiment,force sensation processes can include several different types of stepsand/or instructions. One type of instruction is a force algorithm, whichincludes an equation that host computer 12 can use to calculate or modela force value based on sensor and timing data. Several types ofalgorithms can be used. For example, algorithms in which force varieslinearly (or nonlinearly) with the position of object 34 can be used toprovide a simulated force like a spring. Algorithms in which forcevaries linearly (or nonlinearly) with the velocity of object 34 can bealso used to provide a simulated damping force or other forces.Algorithms in which force varies linearly (or nonlinearly) with theacceleration of object 34 can also be used to provide, for example, asimulated inertial force on a mass (for linear variation) or a simulatedgravitational pull (for nonlinear variation). Several types of simulatedforces and the algorithms used to calculate such forces are described in“Perceptual Design of a Virtual Rigid Surface Contact,” by Louis B.Rosenberg, Center for Design Research, Stanford University, Reportnumber AL/CF-TR-1995-0029, April 1993, which is incorporated byreference herein.

[0091] For force values depending on the velocity and acceleration ofuser object 34, the velocity and acceleration can be provided in anumber of different ways. The sensor data read by host computer 12 instep 78 can include position data, velocity data, and acceleration data.In a preferred embodiment, the velocity and acceleration data wascalculated previously by microprocessor 26 and then provided to the hostcomputer 12. The host computer can thus use the velocity andacceleration data directly in an algorithm to calculate a force value.In an alternate embodiment, the sensor data read in step 78 includesposition data and no velocity or acceleration data, so that hostcomputer 12 is required to calculate the velocity and acceleration fromthe position data. This can be accomplished by recording a number ofpast position values, recording the time when each such position valuewas received using the system clock 18, and calculating a velocityand/or acceleration from such data.

[0092] For example, a kinematic equation which calculates a force basedon the velocity of the user object multiplied by a damping constant canbe used to determine a damping force on the user object. This type ofequation can simulate motion of object 34 along one degree of freedomthrough a fluid or similar material. A procedure for calculating adamping force on object 34 is described in co-pending patent applicationSer. No. 08/400,233, filed Mar. 3, 1995 entitled “Method and Apparatusfor Providing Passive Force Feedback”, which is hereby incorporated byreference herein. For example, a damping constant can first be selectedwhich indicates the degree of resistance that object 34 experiences whenmoving through a simulated material, such as a liquid, where a greaternumber indicates greater resistance. For example, water would have alower damping constant than oil or syrup. The host computer recalls theprevious position of user object 34 (along a particular degree offreedom), examine the current position of the user object, and calculatethe difference in position. From the sign (negative or positive) of thedifference, the direction of the movement of object 34 can also bedetermined. The force is then set equal to the damping constantmultiplied by the change in position. Commands that controlled anactuator based on this algorithm would produce a force proportional tothe user object's motion to simulate movement through a fluid. Movementin other mediums, such as on a bumpy surface, on an inclined plane,etc., can be simulated in a similar fashion using different methods ofcalculating the force.

[0093] The determination of force commands is preferably influenced bytiming data accessed from system clock 18. For example, in the dampingforce example described above, the velocity of the user object 34 isdetermined by calculating the different of positions of the user objectand multiplying by the damping constant. This calculation assumes afixed time interval between data points, i.e., it is assumed that theposition data of the object 34 is received by host computer 12 inregular, predetermined time intervals. However, this may not actuallyoccur due to different processing speeds of different computer platformsor due to processing variations on a single host microprocessor 16, suchas due to multitasking. Therefore, in the present invention, the hostcomputer preferably accesses clock 12 to determine how much time hasactually elapsed since the last position data was received. In thedamping force example, the host computer could take the difference inposition and divide it by a time measure to account for differences intiming. The host computer can thus use the clock's timing data in themodulation of forces and force sensations to the user. Timing data canbe used in other algorithms and force sensation processes of the presentinvention to provide repeatable and consistent force feedback regardlessof type of platform or available processing time on host computer 12.

[0094] Other instructions can also be included in a force sensationprocess. For example, conditions can be included to provide forces onlyin desired directions or under other particular circumstances. Forexample, to simulate a virtual obstruction such as a wall, forces shouldbe applied in only one direction (uni-directional). For many passiveactuators, only bi-directional resistance forces can be applied. Tosimulate uni-direction resistance, conditions can be included in thevirtual obstruction force sensation process. An example of suchconditions in a virtual obstruction force sensation process is describedwith respect to FIG. 12. Also, a “null” reflex process can be availablethat instructs host computer 12 (or microprocessor 26 in the embodimentof FIG. 5) to issue a low level command or force values to provide zeroforces (i.e. remove all forces) on user object 34.

[0095] Another type of force sensation process does not use algorithmsto model a force, but instead uses force values that have beenpreviously calculated or sampled and stored as a digitized “forceprofile” in memory or other storage device. These force values may havebeen previously generated using an equation or algorithm as describedabove, or provided by sampling and digitizing forces. For example, toprovide a particular force sensation to the user, host computer 12 canbe instructed by a force sensation process to retrieve successive forcevalues from a certain storage device, such as RAM, ROM, hard disk, etc.These force values can be sent directly to an actuator in a low-levelcommand to provide particular forces without requiring host computer 12to calculate the force values. In addition, previously-stored forcevalues can be output with respect to other parameters to providedifferent types of forces and force sensations from one set of storedforce values. For example, using system clock 18, the stored forcevalues can be output in sequence according to a particular time intervalthat can vary depending on the desired force. Or, different retrievedforce values can be output depending on the current position of userobject 34.

[0096] Host computer 12 can determine a force command in step 82according to a newly-selected reflex process, or to a previouslyselected reflex process. For example, if this is a second or lateriteration of step 82, the same reflex process as in the previousiteration can be again implemented if parameters (such as the positionof object 34) allow it, as determined by the host application program.

[0097] The force command determined in step 82 can also depend oninstructions that check for other parameters. These instructions can beincluded within or external to the above-described reflex processes. Onesuch parameter are values provided by the implemented host applicationprogram (if any). The application program may determine that aparticular force command should be output or reflex process implementedbased on events occurring within the application program or otherinstructions. Force commands or values can be provided by the hostapplication program independently of sensor data. Also, the hostapplication program can provide its own particular position, velocity,and/or acceleration data to a selected reflex process to calculate orprovide a force that is not based on the manipulation of user object 34,but is provided to simulate an event in the application program. Suchevents may include collision events, such as occur when auser-controlled computer image impacts a virtual surface or structure.Also, other input devices connected to host computer 12 can influenceevents and, therefore, the forces applied to user object 34. Forexample, the sensor data from multiple interface devices 14 connected toa single host computer can influence the forces felt on other connectedinterface devices by influencing events and computer-controlledimages/objects of the host application program.

[0098] Also, the force commands determined in step 82 can be based onother inputs to host computer 12, such as activations of buttons orother input devices in (or external to) interface device 14. Forexample, a particular application program might require that a force beapplied to a joystick whenever a user presses a fire button on thejoystick.

[0099] The above-described reflex processes and other parameters can beused to provide a variety of haptic sensations to the user through theuser object 34 to simulate many different types of tactile events. Forexample, typical haptic sensations may include a virtual damping(described above), a virtual obstruction, and a virtual texture. Virtualobstructions are provided to simulate walls, obstructions, and otheruni-directional forces in a simulation, game, etc. When a user moves acomputer image into a virtual obstruction with a joystick, the user thenfeels a physical resistance as he or she continues to move the joystickin that direction. If the user moves the object away from theobstruction, the uni-directional force is removed. Thus the user isgiven a convincing sensation that the virtual obstruction displayed onthe screen has physical properties. Similarly, virtual textures can beused to simulate a surface condition or similar texture. For example, asthe user moves a joystick or other user object along an axis, the hostcomputer sends a rapid sequence of commands to repetitively 1) applyresistance along that axis, and 2) to then immediately apply noresistance along that axis, as according to a reflex process. Thisfrequency is based upon the travel of the joystick handle and is thuscorrelated with spatial position. Thus, the user feels a physicalsensation of texture, which can be described as the feeling of dragginga stick over a grating.

[0100] In next step 84, a low-level force command determined in step 82is output to microprocessor 26 over bus 24. This force command typicallyincludes a force value that was determined in accordance with theparameters described above. The force command can be output as an,actual force signal that is merely relayed to an actuator 30 bymicroprocessor 26; or, the force command can be converted to anappropriate form by microprocessor 26 before being sent to actuator 30.In addition, the low-level force command preferably includes informationindicating to microprocessor 26 which actuators are to receive thisforce value (if multiple actuators are included on interface device 14).The process then returns to step 76 to process/update the hostapplication program. The process continues to step 80, where the hostcomputer checks if a different force command should be output asdetermined by the parameters described above. If so, a new force commandis determined and output in step 84. If no change of force is required,host computer 12 does not issue another command, since microprocessor 26can continues to output the previous force command to actuators 30(alternatively, host computer 12 can continue to output commands, evenif no change of force is required). Subsequent force commands output instep 84 can be determined in accordance with the same reflex process, ora different reflex process, depending on the parameters of step 82.

[0101] In addition, the host computer 12 preferably synchronizes anyappropriate visual feedback, auditory feedback, or other feedbackrelated to the host application with the application of forces on userobject 34. For example, in a video game application, the onset or startof visual events, such as an object colliding with the user on displayscreen 20, should be synchronized with the onset or start of forces feltby the user which correspond to or complement those visual events. Theonsets visual events and force events are preferably occur within about30 milliseconds (ms) of each other. This span of time is the typicallimit of human perceptual ability to perceive the events assimultaneous. If the visual and force events occur outside this range,then a time lag between the events can usually be perceived. Similarly,the output of auditory signals, corresponding to the onset of auditoryevents in the host application, are preferably output synchronized withthe onset of output forces that correspond to/complement those auditoryevents. Again, the onsets of these events occur preferably within about30 ms of each other. For example, host computer system 12 can outputsounds of an explosion from speakers 21 as close in time as possible tothe forces felt by the user from that explosion in a simulation.Preferably, the magnitude of the sound is in direct (as opposed toinverse) proportion to the magnitude of the forces applied to userobject 34. For example, during a simulation, a low sound of an explosionin the far (virtual) distance can cause a small force on user object 34,while a large, “nearby” explosion might cause a loud sound to be outputby the speakers and a correspondingly large force to be output on object34.

[0102] The local microprocessor 26 implements the process branching fromstep 74 and starting with step 86 in parallel with the host computerprocess described above. In step 86, the interface device 14 isactivated. For example, signals can be sent between host computer 12 andinterface device 14 to acknowledge that the interface device is nowactive. From step 86, two processes branch to indicate that there aretwo processes running simultaneously (multi-tasking) on local processor26. In one process, step 88 is implemented, in which the processor 26reads raw data (sensor readings) from sensors 28. Such raw datapreferably includes position values describing the position of the userobject along provided degrees of freedom. In the preferred embodiment,sensors 28 are relative sensors that provide position values describingthe change in position since the last position read. Processor 26 candetermine the absolute position by measuring the relative position froma designated reference position. In alternate embodiments, sensors 28can include velocity sensors and accelerometers for providing rawvelocity and acceleration values of object 34. The raw data read in step88 can also include other input, such as from an activated button orother control 39 of interface device 14.

[0103] In next step 90, processor 26 processes the received raw datainto sensor data, if applicable. In the preferred embodiment, thisprocessing includes two steps: computing velocity and/or accelerationvalues from raw position data (if velocity and/or acceleration areneeded to compute forces), and filtering the computed velocity andacceleration data. The velocity and acceleration values are computedfrom raw position data received in step 88 and stored position and timevalues. Preferably, processor 26 stores a number of position values andtime values corresponding to when the position values were received.Processor 26 can use its own or a local system clock (not shown inFIG. 1) to determine the timing data. The velocity and acceleration canbe computed using the stored position data and timing data, as is wellknown to those skilled in the art. The calculated velocity and/oracceleration values can then be filtered to remove noise from the data,such as large spikes that may result in velocity calculations from quickchanges in position of object 34. Thus, the sensor data in the describedembodiment includes position, velocity, acceleration, and other inputdata. In an alternate embodiment, circuitry that is electrically coupledto but separate from processor 26 can receive the raw data and determinevelocity and acceleration. For example, an application-specificintegrated circuit (ASIC) or discrete logic circuitry can use countersor the like to determine velocity and acceleration to save processingtime on microprocessor 26.

[0104] Alternatively, step 90 can be omitted, and the processor 26 canprovide raw position data to host computer 12 (and other input data fromother input devices 39). This would require host computer 12 to filterand compute velocity and acceleration from the position data. Thus, itis preferred that processor 26 do this processing to reduce the amountof processing performed on host computer 12. In other embodiments, thefiltering can be performed on host computer 12 while the velocity andacceleration calculation can be performed on the processor 26. Also, inembodiments where velocity and/or acceleration sensors are used toprovide raw velocity and acceleration data, the calculation of velocityand/or acceleration can be omitted. After step 90, step 91 isimplemented, in which the processor 26 sends the processed sensor datato the host computer 12 via bus 24. The process then returns to step 88to read raw data. Steps 88, 90 and 91 are thus continuously implementedto provide current sensor data to host computer system 12.

[0105] The second branch from step 86 is concerned with processor 26controlling the actuators 30 to provide forces calculated by hostcomputer 12 to object 34. The second branch starts with step 92, inwhich processor 26 checks if a low-level force command has been receivedfrom host computer 12 over bus 24. If not, the process continuallychecks for such a force command. When a force command has been received,step 94 is implemented, in which processor 26 outputs a low-levelprocessor force command to the designated actuators to set the outputforce to the desired magnitude, direction, etc. This force command maybe equivalent to the received low-level command from the host computer,or, the processor 26 can optionally convert the force command to anappropriate form usable by actuator 30 (or actuator interface 38 canperform such conversion). The process then returns to step 92 to checkfor another force command from the host computer 12.

[0106]FIG. 5 is a flow diagram illustrating a second embodiment of amethod 100 for controlling force feedback interface device 14 of thepresent invention. Method 100 is directed to a “reflex” embodiment, inwhich host computer system 12 provides only high-level supervisory forcecommands (“host commands”) to microprocessor 26, while themicroprocessor independently determines and provides low-level forcecommands (force values) to actuators 30 as an independent “reflex” tocontrol forces output by the actuators.

[0107] The process of FIG. 5 is suitable for low speed communicationinterfaces, such as a standard RS-232 serial interface. However, theembodiment of FIG. 5 is also suitable for high speed communicationinterfaces such as USB, since the local microprocessor relievescomputational burden from host processor 16. In addition, thisembodiment can provide a straightforward command protocol, an example ofwhich is described with respect to FIGS. 9 and 14, and which allowsoftware developers to easily provide force feedback in a hostapplication. In this embodiment, for example, the slower “interrupt datatransfers” mode of USB can be used.

[0108] The process begins at 102. In step 104, host computer system 12and interface device 14 are powered up, for example, by a useractivating power switches. After step 104, the process 100 branches intotwo parallel processes. One process is implemented on host computersystem 12, and the other process is implemented on local microprocessor26.

[0109] In the host computer system process, step 106 is firstimplemented, in which an application program is processed. Thisapplication can be a simulation, video game, scientific program, orother program. Images can be displayed for a user on output displayscreen 20 and other feedback can be presented, such as audio feedback.

[0110] Two branches exit step 106 to indicate that there are twoprocesses running simultaneously (multi-tasking, etc.) on host computersystem 12. In one of the processes, step 108 is implemented, wheresensor data from the user object is received by the host computer fromlocal microprocessor 26. Similarly to step 78 of the process of FIG. 4,host computer system 12 receives either raw data (e.g., position dataand no velocity or acceleration data) or processed sensor data(position, velocity and/or acceleration data) from microprocessor 26. Inaddition, any other data received from other input devices 39 can alsobe received by host computer system 12 from microprocessor 26 in step108, such as signals indicating a button on interface device 14 has beenpressed by the user.

[0111] Unlike the previous embodiment of FIG. 4, the host computer doesnot calculate force values from the received sensor data in step 108.Rather, host computer 12 monitors the sensor data to determine when achange in the type of force is required. This is described in greaterdetail below. Of course, host computer 12 also uses the sensor data asinput for the host application to update the host applicationaccordingly.

[0112] After sensor data is received in step 108, the process returns tostep 106, where the host computer system 12 can update the applicationprogram in response to the user's manipulations of object 34 and anyother user input received in step 108. Step 108 is then implementedagain in a continual loop of receiving sets of sensor data from localprocessor 26. Since the host computer does not need to directly controlactuators based on sensor data, the sensor data can be provided at amuch lower speed. For example, since the host computer updates the hostapplication and images on display screen 20 in response to sensor data,the sensor data need only be read at 60-70 Hz (the refresh cycle of atypical display screen) compared to the much higher rate of about500-1000 Hz (or greater) needed to realistically provide low-level forcefeedback signals from sensor signals. Host computer 12 also preferablysynchronizes visual, audio, and force events similarly as describedabove with reference to FIG. 4.

[0113] The second branch from step 106 is concerned with the process ofthe host computer determining high-level force commands (“hostcommands”) to provide force feedback to the user manipulating object 34.The second branch starts with step 110, in which the host computersystem checks if a change in the type of force applied to user object 34is required. The “type” of force is a force sensation or profileproduced by a particular reflex process or force value which the localmicroprocessor 26 can implement independently of the host computer. Thehost computer 12 determines whether a change in the type of force isrequired depending on the sensor data read by the host computer in step108 and depending on the events of the application program updated instep 106. As explained with reference to FIG. 4, the sensor data informsthe host computer when forces should be applied to the object based onthe object's current position, velocity, and/or acceleration. The user'smanipulations of object 34 may have caused a new type of force torequired. For example, if the user is moving a virtual race car within avirtual pool of mud in a video game, a damping type of force should beapplied to the object 34 as long as the race car moves within the mud.Thus, damping forces need to be continually applied to the object, butno change in the type of force is required. When the race car moves outof the pool of mud, a new type of force (i.e. a removal of damping forcein this case) is required. The events of the application program mayalso require a change in the type of force applied. For example, if theuser's car is travelling through mud and another car collides into theuser's car, then a new type of force (collision force) should be appliedto the user object. Forces may be required on the user object dependingon a combination of an application event and the sensor data read instep 108. Also, other input, such as a user activating buttons or otherinput devices 39 on interface device 14, can change the type of forcesrequired on object 34.

[0114] If no change in the type of force is currently required in step110, then the process returns to step 106 to update the host applicationand return to step 110 to again check until such a change the type offorce is required. When such a change is required, step 112 isimplemented, in which host computer 12 determines an appropriate hostcommand to send to microprocessor 26. The available host commands forhost computer 12 may each correspond to an associated reflex processimplemented by microprocessor 26. For example, host commands to providea damping force, a spring force, a gravitational pull, a bumpy surfaceforce, a virtual obstruction force, and other forces can be available tohost computer 12. These host commands can also include a designation ofthe particular actuators 30 or degrees of freedom which are to applythis desired force on object 34. The host commands can also includeother command parameter information which might vary the force producedby a particular reflex process. For example, a damping constant can beincluded in a host command to designate a desired amount of dampingforce. The host command may also preferably override the reflexoperation of the processor 26 and include low-level force values. Apreferred command protocol and detailed description of a set of hostcommands is described in greater detail below with respect to FIGS. 9and 14. In next step 114, the host computer sends the host command tothe microprocessor 26 over bus 24. The process then returns to step 106to update the host application and to return to step 110 to check ifanother change in force is required.

[0115] The local microprocessor 26 implements the process branching fromstep 104 and starting with step 116 in parallel with the host computerprocess described above. In step 116, the interface device 14 isactivated. For example, signals can be sent between host computer 12 andinterface device 14 to acknowledge that the interface device is nowactive and can be commanded by host computer 12. From step 116, twoprocesses branch to indicate that there are two processes runningsimultaneously (multi-tasking) on local processor 26. In one process,step 118 is implemented, in which the processor 26 reads raw data fromsensors 28. As described in step 88 of FIG. 4, processor 26 preferablyreads position data and no velocity or acceleration data from sensors28. In alternate embodiments, sensors 28 can include velocity sensorsand accelerometers for providing velocity and acceleration values ofobject 34. The sensor data read in step 118 can also include otherinput, such as from an activated button or other control of interfacedevice 14.

[0116] In next step 120, processor 26 processes the received raw datainto sensor data. As described in step 90 of FIG. 4, this processingpreferably includes the two steps of computing velocity and accelerationdata from the filtered position data and filtering the velocity andacceleration data. Processor 26 can use its own local clock 21 todetermine the timing data needed for computing velocity andacceleration. In addition, a history of previous recorded values, suchas position or velocity values, can be used to calculate sensor data. Inembodiments where velocity and/or acceleration sensors are used, thecalculation of velocity and/or acceleration is omitted. In next step121, the processor 26 sends the processed sensor data to host computer12 and also stores the data for computing forces, as described in thesecond branch process of processor 26. The process then returns to step118 to read raw data. Steps 118, 120 and 121 are thus continuouslyimplemented to provide current sensor data to processor 26 and hostcomputer 12.

[0117] The second branch from step 116 is concerned with an “actuatorprocess” in which processor 26 controls the actuators 30 to provideforces to object 34. The second branch starts with step 122, in whichprocessor 26 checks if a host command has been received from hostcomputer 12 over bus 24. If so, the process continues to step 124, wherea reflex process associated with the host command is selected. Suchreflex processes can be stored local to microprocessor 26 in, forexample, memory 27 such as RAM or ROM (or EPROM, EEPROM, etc.). Thus,the microprocessor might select a damping reflex process if the highlevel command indicated that the damping force from this reflex processshould be applied to object 34. The available reflex processes arepreferably similar to those described above with reference to FIG. 4,and may include algorithms, stored force profiles or values, conditions,etc. In some embodiments, steps 118, 120, and 121 for reading sensordata can be incorporated in the reflex processes for the microprocessor,so that sensor data is only read once a reflex process has beenselected. Also, the host command may in some instances simply be alow-level force command that provides a force value to be sent to anactuator 30 (as in the embodiment of FIG. 4), in which case a reflexprocess need not be selected.

[0118] After a reflex process has been selected in step 124, or if a newhost command has not been received in step 122, then step 126 isimplemented, in which processor 26 determines a processor low-levelforce command (i.e. force value). The force value is derived from thereflex process and any other data required by the reflex process as wellas command parameters included in relevant host commands. As explainedabove, the needed data can include sensor data and/or timing data fromlocal clock 29. Thus, if no new high level command was received in step122, then the microprocessor 26 determines a force command according tothe same reflex process that it was previously using in step 126. Inaddition, the host command can include other command parameterinformation needed to determine a force command. For example, the hostcommand can indicate the direction of a force along a degree of freedom.

[0119] In step 128, processor 26 outputs the determined processor forcecommand to actuators 30 to set the output force to the desired level.Before sending out the force command, processor 26 can optionallyconvert the force command to an appropriate form usable by actuator 30,or actuator interface 38 can perform such conversion. The process thenreturns to step 122 to check if another host command has been receivedfrom the host computer 12.

[0120] The actuator process of microprocessor 26 (steps 118, 120, 122,124, 126, and 128) thus operates to provide forces on object 34independently of host computer 12 according to a selected reflex processand other parameters. The reflex process determines how the processorforce command is to be determined based on the most recent sensor dataread by microprocessor 26. Since a reflex process indicates how forcesshould be applied depending on the position and other parameters of userobject 34, the processor can issue low-level force commands, freeing thehost computer to process the host application and determine only when anew type of force needs to be output. This greatly improvescommunication rates between host computer 12 and interface device 14.

[0121] In addition, the host computer 12 preferably has the ability tooverride the reflex operation of microprocessor 26 and directly providecalculated or other force values as described above with reference toFIG. 4. For example, the host command can simply indicate a force valueto be sent to an actuator 30. This override mode can also be implementedas a reflex process. For example, the microprocessor 26 can select areflex process that instructs it to relay low-level force commandsreceived from host computer 12 to an actuator 30.

[0122]FIG. 6 is a schematic diagram of an example of a user object 34that is coupled to a gimbal mechanism 140 for providing two or morerotary degrees of freedom to object 34. Gimbal mechanism 140 can becoupled to interface device 14 or be provided with sensors 28 andactuators 30 separately from the other components of interface device14. A gimbal device as shown in FIG. 6 is described in greater detail inco-pending patent application Ser. Nos. 08/374,288 and 08/400,233, filedon Jan. 18, 1995 and Mar. 3, 1995, respectively, and hereby incorporatedby reference herein.

[0123] Gimbal mechanism 140 can be supported by a grounded surface 142,which can be a surface of the housing of interface device 14, forexample (schematically shown as part of member 144). Gimbal mechanism140 is preferably a five-member linkage that includes a ground member144, extension members 146 a and 146 b, and central members 148 a and148 b. Ground member 144 is coupled to abase or surface which providesstability for mechanism 140. The members of gimbal mechanism 140 arerotatably coupled to one another through the use of bearings or pivots,wherein extension member 146 a is rotatably coupled to ground member 144and can rotate about an axis A, central member 148 a is rotatablycoupled to extension member 146 a and can rotate about a floating axisD, extension member 146 b is rotatably coupled to ground member 144 andcan rotate about axis B, central member 148 b is rotatably coupled toextension member 146 b and can rotate about floating axis E, and centralmember 148 a is rotatably coupled to central member 148 b at a centerpoint P at the intersection of axes D and E. The axes D and E are“floating” in the sense that they are not fixed in one position as areaxes A and B. Axes A and B are substantially mutually perpendicular.

[0124] Gimbal mechanism 140 is formed as a five member closed chain.Each end of one member is coupled to the end of a another member. Thefive-member linkage is arranged such that extension member 146 a,central member 148 a, and central member 148 b can be rotated about axisA in a first degree of freedom. The linkage is also arranged such thatextension member 146 b, central member 148 b, and central member 148 acan be rotated about axis B in a second degree of freedom.

[0125] User object 34 is a physical object that can be coupled to alinear axis member 150, or linear axis member 150 can be considered partof object 34. Linear member 150 is coupled to central member 148 a andcentral member 148 b at the point of intersection P of axes D and E.Linear axis member 150 is coupled to gimbal mechanism 140 such that itextends out of the plane defined by axis D and axis E. Linear axismember 150 can be rotated about axis A (and E) by rotating extensionmember 146 a, central member 148 a, and central member 148 b in a firstrevolute degree of freedom, shown as arrow line 151. Member 150 can alsobe rotated about axis B (and D) by rotating extension member 50 b andthe two central members about axis B in a second revolute degree offreedom, shown by arrow line 152. In alternate embodiments, linear axismember is also translatably coupled to the ends of central members 148 aand 148 b, and thus can be linearly moved along floating axis C,providing a third degree of freedom as shown by arrows 153. Axis C can,of course, be rotated about one or both axes A and B as member 150 isrotated about these axes. In addition, linear axis member 150 in someembodiments can rotated about axis C, as indicated by arrow 155, toprovide an additional degree of freedom. These additional degrees offreedom can also be provided with sensors and actuators to allowprocessor 26/host computer 12 to read the position/motion of object 34and apply forces in those degrees of freedom.

[0126] Sensors 28 and actuators 30 can be coupled to gimbal mechanism140 at the link points between members of the apparatus and provideinput to and output as described above. Sensors and actuators can becoupled to extension members 146 a and 146 b, for example.

[0127] User object 34 is coupled to mechanism 140. User object 44 may bemoved in both (or all three or four) degrees of freedom provided bygimbal mechanism 140 and linear axis member 150. As object 34 is movedabout axis A, floating axis D varies its position, and as object 34 ismoved about axis B, floating axis E varies its position.

[0128]FIG. 7 is a perspective view of a specific embodiment of anapparatus 160 including gimbal mechanism 140 and other components ofinterface device 14 for providing mechanical input and output to hostcomputer system 12. Apparatus 160 includes gimbal mechanism 140, sensors141 and actuators 143. User object 34 is shown in this embodiment as ajoystick having a grip portion 162 and is coupled to central member 148a. Apparatus 160 operates in substantially the same fashion as gimbalmechanism 140 described with reference to FIG. 6.

[0129] Gimbal mechanism 140 provides support for apparatus 160 ongrounded surface 142, such as a table top or similar surface. Themembers and joints (“bearings”) of gimbal mechanism 140 are preferablymade of a lightweight, rigid, stiff metal, such as aluminum, but canalso be made of other rigid materials such as other metals, plastic,etc. Gimbal mechanism 140 includes ground member 144, capstan drivemechanisms 164, extension members 146 a and 146 b, central drive member148 a, and central link member 148 b. Ground member 144 includes a basemember 166 and vertical support members 168. Base member 166 is coupledto grounded surface 142. A vertical support member 168 is coupled toeach of these outer surfaces of base member 166 such that verticalmembers 168 are in substantially 90-degree relation with each other.

[0130] A capstan drive mechanism 164 is preferably coupled to eachvertical member 168. Capstan drive mechanisms 164 are included in gimbalmechanism 140 to provide mechanical advantage without introducingfriction and backlash to the system. The capstan drive mechanisms 164are described in greater detail in co-pending patent application Ser.No. 08/400,233.

[0131] Extension member 146 a is rigidly coupled to a capstan drum 170and is rotated about axis A as capstan drum 170 is rotated. Likewise,extension member 146 b is rigidly coupled to the other capstan drum 170and can be rotated about axis B. Central drive member 148 a is rotatablycoupled to extension member 146 a, and central link member 148 b isrotatably coupled to an end of extension member 146 b. Central drivemember 148 a and central link member 148 b are rotatably coupled to eachother at the center of rotation of the gimbal mechanism, which is thepoint of intersection P of axes A and B. Bearing 172 connects the twocentral members 148 a and 148 b together at the intersection point P.

[0132] Gimbal mechanism 140 provides two degrees of freedom to an object34 positioned at or near to the center point P of rotation. An object ator coupled to point P can be rotated about axis A and B or have acombination of rotational movement about these axes. In alternateembodiments, object 34 can also be rotated or translated in otherdegrees of freedom, such as a linear degree of freedom along axis C or arotary degree of freedom about axis C.

[0133] Sensors 141 and actuators 143 are preferably coupled to gimbalmechanism 140 to provide input and output signals between apparatus 160and microprocessor 26. In the described embodiment, sensors 141 andactuators 143 are combined in the same housing as grounded transducers174. Preferably, transducers 174 a and 174 b are bi-directionaltransducers having optical encoder sensors 141 and active DC servomotors 143. Passive actuators can also be used. The housing of eachgrounded transducer 174 a is preferably coupled to a vertical supportmember 168 and preferably includes both an actuator 143 for providingforce in or otherwise influencing the first revolute degree of freedomabout axis A and a sensor 141 for measuring the position of object 34 inor otherwise influenced by the first degree of freedom about axis A. Arotational shaft of actuator 174 a is coupled to a pulley of capstandrive mechanism 164 to transmit input and output along the first degreeof freedom. Grounded transducer 174 b preferably corresponds to groundedtransducer 174 a in function and operation. Transducer 174 b is coupledto the other vertical support member 168 and is an actuator/sensor whichinfluences or is influenced by the second revolute degree of freedomabout axis B.

[0134] The transducers 174 a and 174 b of the described embodiment areadvantageously positioned to provide a very low amount of inertia to theuser handling object 34. Transducer 174 a and transducer 174 b aredecoupled, meaning that the transducers are both directly coupled toground member 144 which is coupled to ground surface 142, i.e. theground surface carries the weight of the transducers, not the userhandling object 34. The weights and inertia of the transducers 174 a and174 b are thus substantially negligible to a user handling and movingobject 34. This provides a more realistic interface to a virtual realitysystem, since the computer can control the transducers to providesubstantially all of the forces felt by the user in these degrees ofmotion. Apparatus 160 is a high bandwidth force feedback system, meaningthat high frequency signals can be used to control transducers 174 andthese high frequency signals will be applied to the user object withhigh precision, accuracy, and dependability. The user feels very littlecompliance or “mushiness” when handling object 34 due to the highbandwidth. In contrast, in typical prior art arrangements ofmulti-degree of freedom interfaces, one actuator “rides” upon anotheractuator in a serial chain of links and actuators. This low bandwidtharrangement causes the user to feel the inertia of coupled actuatorswhen manipulating an object.

[0135] Object 34 is shown in FIG. 3 as a joystick having a grip portion126 for the user to grasp. A user can move the joystick about axes A andB. The movements in these two degrees of freedom are sensed by processor26 and host computer system 12. Forces can be applied preferably in thetwo degrees of freedom to simulate various haptic sensations.Optionally, other objects 34 can be coupled to gimbal mechanism 140, asdescribed above. For example, medical instruments, such as laparoscopictools or catheters, can be used to simulate medical procedures. Alaparoscopic tool sensor and force feedback device is described in U.S.patent application Ser. No. 08/275,120, filed Jul. 14, 1994 and entitled“Method and Apparatus for Providing Mechanical I/O for Computer Systems”assigned to the assignee of the present invention and incorporatedherein by reference in its entirety.

[0136]FIG. 8 is a perspective view of a different embodiment of object34 and supporting mechanism 180 that can be used in conjunction withinterface device 14. Mechanism 180 includes a slotted yoke configurationfor use with joystick controllers that is well-known to those skilled inthe art. Mechanism 180 includes slotted yoke 182 a, slotted yoke 182 b,sensors 184 a and 184 b, bearings 186 a and 186 b, actuators 188 a and188 b, and joystick 34. Slotted yoke 182 a is rigidly coupled to shaft189 a that extends through and is rigidly coupled to sensor 184 a at oneend of the yoke. Slotted yoke 182 a is similarly coupled to shaft 189 cand bearing 186 a at the other end of the yoke. Slotted yoke 182 a isrotatable about axis L and this movement is detected by sensor 184 a.Actuator 188 a can be an active or passive actuator. In alternateembodiments, bearing 186 a and be implemented as another sensor likesensor 184 a.

[0137] Similarly, slotted yoke 182 b is rigidly coupled to shaft 189 band sensor 184 b at one end and shaft 189 d and bearing 186 b at theother end. Yoke 182 b can rotated about axis M and this movement can bedetected by sensor 184 b.

[0138] Object 34 is a joystick that is pivotally attached to groundsurface 190 at one end 192 so that the other end 194 typically can movein four 90-degree directions above surface 190 in two degrees of freedom(and additional directions in other embodiments). Joystick 34 extendsthrough slots 196 and 198 in yokes 182 a and 182 b, respectively. Thus,as joystick 34 is moved in any direction, yokes 182 a and 182 b followthe joystick and rotate about axes L and M. Sensors 184 a-d detect thisrotation and can thus track the motion of joystick 34. Actuators 188 aand 188 b allow the user to experience force feedback when handlingjoystick 34. Alternatively, other types of objects 34 can be used inplace of the joystick, or additional objects can be coupled to thejoystick. In yet other embodiments, additional degrees of freedom can beprovided to joystick 34. For example, the joystick can be provided witha rotary degree of freedom about axis K, as indicated by arrow 193.Sensors and/or actuators can also be included for such additionaldegrees of freedom.

[0139] In alternate embodiments, actuators can be coupled to shafts 189c and 189 d to provide additional force to joystick 34. Actuator 188 aand an actuator coupled to shaft 189 c can be controlled simultaneouslyby microprocessor 26 or host computer 12 to apply or release force frombail 182 a. Similarly, actuator 188 b and an actuator coupled to shaft189 d can be controlled simultaneously.

[0140] Other embodiments of interface apparatuses and transducers canalso be used in interface device 14 to provide mechanical input/outputfor user object 34. For example, interface apparatuses which provide oneto three (or more) linear degrees of freedom to user object 34 can beused. In addition, passive actuators having an amount of “play” can beprovided to implement different reflex processes. Other embodiments ofactuators and interfaces are described in co-pending patent applicationSer. No. 08/400,233, filed Mar. 3, 1995, entitled “Method and Apparatusfor Providing Passive Force Feedback to Human-Computer InterfaceSystems”, and Ser. No. 08/489,068, filed Jun. 9, 1995, entitled “Methodand Apparatus for Providing Passive Fluid Force Feedback”, both herebyincorporated by reference herein.

[0141]FIG. 9 is a table 300 showing a number of preferred host commandsthat can be used in the embodiment of FIG. 5, where host computer 12sends high level host commands to local microprocessor 26, whichimplements local reflex processes or reflex processes in accordance withthe host commands. As discussed previously, low communication rates onbus 24 (FIG. 1) can impede performance, specifically the accuracy andrealism, of force feedback. The local microprocessor can implementreflex processes based on host commands independently of the hostcomputer, thus requiring less signals to be communicated over bus 24.Preferably, a communication language or force feedback protocol shouldbe standardized for the transfer of host commands from the hostprocessor 16 to the local processor 26. Ideally, as discussed withreference to FIG. 5, the format will permit the efficient transmissionof high level supervisory commands (host commands) to local processor 26as in step 114 of FIG. 5. By providing a relatively small set ofcommands and command parameters which are translated into a panoply offorces, the format further shifts the computational burden from the hostcomputer to the local microprocessor 26. In addition, a programmer ordeveloper of force feedback application software for host computer 12 isprovided with a high level, standard, efficient force feedback commandprotocol.

[0142] In one embodiment, the host command is permitted to includecommand parameters generic to a wide variety of force models implementedby the microprocessor 26 to control the actuators 30. For instance,force magnitude and force direction are two generic command parameters.Force duration, or force model application time, is another genericcommand parameter. It may also be advantageous to further define acommand parameter for other input device 39, such as a button. Thebutton, when activated, can trigger different forces or force models.

[0143] A preferred embodiment contains two primary modes or “controlparadigms” of operation for force feedback interface device 14: ratecontrol and position control. These modes imply a classification schemefor host commands parametrized by the command parameters. While thedifference between rate control and position control is generally subtleto the user while he or she interacts with an application, thedifference may be profound when representing force feedback information.While certain force feedback entities may be implemented under bothcontrol modes, classifying the force feedback commands into two sets canhelp to avoid confusion among programmers. Some of the commands can beused as either rate control or position control commands.

[0144] Exemplary force feedback commands in accordance with the presentinvention will be described below. The rate control force feedbackcommands will be discussed first, followed by the position controlcommands. Of course, other force feedback commands may be constructed inaddition to, or as alternatives to, the following sample force feedbackcommands.

[0145] Rate control refers to a user object mapping in which thedisplacement of the user object 34 along one or more provided degrees offreedom is abstractly mapped to motion of a computer-simulated entityunder control, such as an airplane, race car, or other simulated“player” or player-controlled graphical object. Rate control is anabstraction which makes force feedback less intuitive because there isnot a direct physical mapping between object motion and commanded motionof the simulated computer entity. Nevertheless, many interesting forcefeedback sensations can be implemented within rate control paradigms. Incontrast, position control refers to a user object mapping in whichdisplacement of the joystick handle or other user manipulable objectdirectly dictates displacement of a simulated computer entity, so thatthe fundamental relation between joystick displacements and computerdisplacements is present. Thus, most rate control paradigms arefundamentally different from position control in that the user object(joystick) can be held steady at a given position but the simulatedentity under control is in motion at a given commanded velocity, whilethe position control paradigm only allows the entity under control to bein motion if the user object is in motion. Position control hostcommands are described in greater detail below with respect to FIG. 14,while rate control commands are described presently with reference toFIG. 9.

[0146] For example, a common form of rate control is a velocity derivedabstraction in which displacement of the user object, such as a joystickhandle, dictates a velocity of the simulated computer entity, such as avehicle or other graphical object displayed on display screen 20, in asimulated environment. The greater the joystick handle is moved from theoriginal position, the greater the velocity of the controlled vehicle orplayer-controlled graphical object. Such control paradigms are verypopular in computer games where velocity of a spacecraft or race car isdictated by the displacement of the joystick. Like most rate controlparadigms, velocity control allows the joystick to be held steady at agiven position while the entity under control is in motion at a givencommanded velocity. Other common rate control paradigms used in computergames are acceleration controlled. An acceleration controlled paradigmis termed “thrust” control by those skilled in the art. While velocitycontrol dictates the speed of the entity under control, thrust controldictates the rate of change of speed. Under thrust control, the joystickcan be still and centered at zero displacement, yet the commandedcomputer entity can be in motion.

[0147] In force feedback schemes, rate control force feedback commandsroughly correspond to forces which would be exerted on a vehicle orother simulated entity controlled by the simulated environment throughthe force feedback interface device 14. Such forces are termedvehicle-centric forces. For example, in a thrust control paradigm, auser's simulated speed boat may move into thick mud, but the user wouldnot directly feel the mud. However, the user would feel the speed boat'sengine straining against a force opposing the boat's motion. Theseopposing forces are relayed to the user through interface device 14.Other simulated characteristics or objects in the simulated environmentcan have an effect on the player-controlled simulated entity and thusaffect the forces output to the user.

[0148] Herein, rate control commands are divided into “conditions” and“overlays,” although other classifications may be used in alternateembodiments. Conditions set up a basic physical model or backgroundsensations about the user object including simulated stiffness,simulated damping, simulated inertias, deadbands where simulated forcesdiminish, and directional constraints dictating the physical model'sfunctionality. Multiple conditions may be specified in a single commandto effectively superpose condition forces. Overlays, in contrast, areforces that may be applied in addition to the conditions in thebackground. Any number of overlays can preferably be provided inaddition to condition forces. A condition can be specified by onecondition command or by multiple condition commands.

[0149] Descriptions will now be provided for several types of forces302, as referenced in table 300, that can be implemented bymicroprocessor 26 from host commands. These forces include: restoringforce, restoring spring, vector force, vibration, sluggish stick,wobble, unstable, button reflex jolt, and ratchet force. The restoringforce, restoring spring, sluggish stick, and unstable forces areconsidered condition forces. The vector force, vibration, wobble, buttonreflex jolt, and ratchet forces are considered overlay forces.

[0150] The forces 302 shown in table 300 can be implemented with hostcommands provided by host computer 12 to microprocessor 26. Examples 304of host commands and their syntax are shown in table 300 for each typeof force 302. In the described embodiment, host commands 304 preferablyinclude a command portion 306 and a number of command parameters 308.Commands 304 indicate the type of force which the host computer 12 isinstructing the processor 26 to implement. This command portion may havea corresponding reflex process which the processor 26 can retrieve frommemory 27 and implement; this process is described in greater detailbelow. Command portions 306 can be specified in virtually any form inother embodiments; in table 300, a command is typically provided in ahigh-level form, close to English, so that the type of force which thecommand implements can be easily recognized by a programmer or softwaredeveloper.

[0151] Command parameters 304 are values or indicators provided by thehost computer 12 which customize and/or modify the type of forceindicated by command portion 304. Many of the commands use magnitude,duration, or direction command parameters. Some commands include a styleparameter which often modifies a force's direction. Other particularcommand parameters are provided for specific forces, as described indetail below.

[0152] For the following preferred rate control embodiments, most of thecommand parameters control different forces in the same way. Themagnitude parameter is a percentage of a maximum magnitude correspondingto a maximum force able to be output by actuators 30. The durationparameter usually corresponds to a time interval for applying theparticular force model. However, it is sometimes set to a predeterminedvalue, such as zero or −1, to extend indefinitely the force model'sapplication time. The force model would thus remains in effect until thehost computer 12 provides a new host command with a new force or sends aclear command. The style parameter may select a direction in which toapply the force model, and/or a degree of freedom along which to applythe force model. For example, valid directions usually include one of acommon joystick's two axes or a diagonal specified as a combination ofthe two. Of course, the style parameter could specify the forceapplication along any degree of freedom or combination of degrees offreedom. Alternatively, separate force commands could be used for eachdegree of freedom or force commands. The style parameter can varydepending on the particular force model commanded, as described below.

[0153] Although not listed in FIG. 9, all of the described types offorces 302 can have additional parameters or incorporate otherproperties into the listed parameters. A “deadband” parameter couldspecify a size of a region where a force would be small or zero. Aparameter can be included indicating whether a force is bi-directionalor uni-directional along a degree of freedom. Note that uni-directionalforces can have either a positive or negative sense. For some hostcommands, the deadband and bi-directional/uni-directional parameter canbe included in the style parameter.

[0154] Subclass 310 indicates a classification of the types of forces302. Forces 302 are shown as either conditions or overlays, as explainedabove. The condition commands are described below before the overlaycommands.

[0155]FIGS. 10a-c are graphs illustrating force versus displacementprofiles for a restoring force. The force in graph 312 of FIG. 10a isbi-directional, where the force on the right side of the vertical axisis applied in one direction along a degree of freedom, and the force onthe left side of the vertical axis is applied in the opposite directionalong that degree of freedom. The force shown in graph 314 of FIG. 10bis uni-directional. Preferably, whether the force is uni-directional orbi-directional is specified with, for example, the style parameter 308of the command 306 shown in table 300 of FIG. 8 (and, if uni-direction,a positive or negative sense to indicate the particular direction). Inaddition, the desired degrees of freedom along which the restoring forceis to be applied are also preferably specified in the style parameter.For example, an “X” parameter could indicate the “X” degree of freedom,while an “XY” parameter can indicate a restoring force along both X andY degrees of freedom (e.g., a diagonal restoring force).

[0156] A restoring force applied to user object 34 always points backtowards an origin position O (or “neutral position”) of the user objectalong a degree of freedom. For example, the origin position for ajoystick can be the joystick's center position, as shown in FIGS. 7 and8. The magnitude of restoring force, specified by the magnitude commandparameter, generally remains constant in either direction for the range316 along the degree of freedom of the user object. The maximum forcemagnitude F is preferably limited to about 75% of the maximum possibleoutput force in a the selected degree of freedom, so that jolts andvibrations can be overlaid on top of the restoring sensation (describedbelow). As the object is moved toward the origin position O, the appliedforce is constant until the user object is moved within a localizedregion R about the origin position. When the user object is in thelocalized region R, the applied force rapidly drops to zero or a smallvalue. Thus, the restoring force profile provides a constant “restoringsensation” that forces the user object back to the origin position whenthe object is in range 316. This restoring forces then diminishes orvanishes as the object nears and reaches the origin position. Therestoring force's direction can be automatically controlled by the localmicroprocessor 26.

[0157] In FIG. 10c, the restoring force is shown similarly to the forcein FIG. 10a, except that the applied force is about zero in an extendedregion 318, about the origin position. Region 318 is known as a“deadband”, and allows the user to have some freedom to move object 34for a short distance around the origin before forces are applied. Thespecification of deadband 318 for an applied restoring force can be avalue included, for example, as a separate deadband command parameter,or, alternatively, as part of the style parameters 308 of the restoringforce host command.

[0158] A restoring force sensation can be very ably applied in a ratecontrol paradigm to the situation of hitting a wall or some otherobstruction while controlling a simulated vehicle. The restoring forceindicates a resistance against commanding a velocity in a direction ofmotion. This force drops off when the user object is returned to theorigin position because the user is no longer commanding a velocity inthe direction of motion. If there is no obstruction in the reversedirection, the restoring force would be unidirectional.

[0159]FIGS. 11a-11 c are graphs illustrating force versus displacementprofiles for a restoring spring force. Rather than maintaining aconstant magnitude over its positive or negative displacement, asprovided by the restoring force of FIGS. 10a-10 c, a restoring springforce varies linearly over an appreciable portion of the user object'sdisplacement, and is proportional to the object 34's distance from theorigin position O. A restoring spring force applied to the user objectalways points back towards the neutral position along a degree offreedom. In FIGS. 11a-11 c the restoring spring force reaches itsmaximum at maximum displacement of object 34 from the origin position O.Graph 320 of FIG. 11a shows the bi-directional case, and graph 322 ofFIG. 11b shows the uni-directional case. A deadband specified by adeadband parameter is provided about the origin position, as shown ingraph 324 of FIG. 11c.

[0160] The parameters for the restoring spring force can, for example,be substantially similar to the parameters for the restoring force asdescribed above. Alternatively, instead of a magnitude parameter, therestoring spring force can have a spring coefficient parameter todescribe a desired “stiffness” of the object 34. The spring coefficientparameter can be used in well known equations to calculate the force onthe user object. Either the coefficient or magnitude parameter may beused.

[0161] The sluggish force creates a damping force on user object 34having a magnitude proportional to the velocity of the user object whenmoved by the user. An example of this type of damping force is describedabove with respect to step 82 of FIG. 4. The degree of “viscosity” ofthe sluggish force can be specified by a viscous damping coefficientincluded as a command parameter in the host command. Since the sluggishstick force depends directly upon velocity, the coefficient commandparameter can be expressed as a percentage of a maximum dampingcoefficient, and replaces the magnitude parameter of previouslydiscussed host commands. The style command parameter for the sluggishhost command can include the specified degrees of freedom to apply thesluggish force, as well as a uni-directional or bi-directionalindication. The sluggish stick force is particularly suited for ratecontrol applications to simulate controlling, for example, a very heavyvehicle that is poorly responsive to the movement of the user object.

[0162] The unstable force creates an inverted pendulum styleinstability. Alternatively, the unstable force is modelled on a springhaving a negative spring constant (an unstable or diverging spring). Aforce is applied to the user object in a direction away from theobject's origin position and is increased as the user object is movedfurther away from the origin position. This creates a force that makesit difficult for the user to bring the object to the origin position.The command parameters for an unstable host command can include similarparameters to the restoring forces described above; for example, acommand parameter indicating the percentage of maximum degree of“instability” can be provided, where the instability can be defined interms of a maximum output force. This force can be used as anothervehicle-related sensation, and could replace a restoring spring forcewhen, for example, a simulated vehicle guidance control is damaged. Theinstability would typically make a computer game very hard to play.

[0163] In alternative embodiments, the condition forces described abovecan be commanded using only one host command with a number of parametersto control the characteristics of the condition forces. For example, ahost command such as

COND_X (K+, K−, DB, B+, B−, N_Offset, Sat+, Sat−, m)

[0164] can be sent to microprocessor 26 from host computer 12. Thiscommand specifies certain physical parameters of a model of the userobject in one degree of freedom. The K parameters indicate aproportional stiffness for displacements of the user object in twodirections along a degree of freedom. The DB parameter indicates thedeadband range as a percentage of a maximum allowed deadband distance.The B parameters indicate a velocity proportional damping for thevelocity of the user object in two directions along a degree of freedom.The N_offset parameter can be specified as the offset from the modeledneutral position of the springs (defined by the K parameters). The Satparameters indicate the maximum (saturation) allowed force value fordisplacements of the user object, expressed, for example, as apercentage of the maximum possible force. The m parameter indicates asimulated mass of the user object which can be applied in the physicalmodel for computing gravitational or inertial forces on the user object,for example. A condition command as provided above can be used for eachprovided degree of freedom of user object 34; for example, COND_X canprovide the condition forces in the degree of freedom about the x-axis.The command can implement the restoring force, restoring spring force,sluggish force, and unstable force by adjusting the various commandparameters.

[0165] The condition commands can be provided in the background whileoverlay commands are applied in addition to or “over” the conditionforces. For example, a sluggish damping force can be provided as abackground force to the user object, and a “jolt” overlay force can becommanded over the sluggish force to provide a quick, jerky motion onthe user object for a few seconds. Of course, overlay forces may also beapplied exclusively when no other forces are being applied, or maycancel other previously-commanded forces if desired. The example overlayforces shown in FIG. 9 are described below.

[0166]FIG. 12 is a graph 326 illustrating a vector force model. A vectorforce is an overlay command, and thus can be applied in addition to thecondition forces described above. It is a general force applied to thejoystick in a given direction specified by a direction commandparameter. The direction command parameter can be provided, for example,as an angle in the X-Y plane for a two-degree-of-freedom interfaceapparatus. As for many of the condition force commands, the magnitude ofthe vector force can be specified as a percentage of a maximummagnitude. FIG. 12 shows a two-dimensional representation of the vectorforce in an example direction in the X-Y plane of a user object havingtwo degrees of freedom.

[0167]FIGS. 13a-13 b are graphs illustrating force versus time profilesfor a vibration force. FIG. 13a is a graph 328 showing a bi-directionalvibration force while FIG. 13b is a graph 330 showing a uni-directionalvibration force. The vibration command shown in FIG. 9 acceptsmagnitude, frequency, style, direction, and duration command parameters.The frequency parameter can be implemented as a percentage of a maximumfrequency and is inversely proportional to a time interval of oneperiod, T_(P). The direction command parameter can be implemented as anangle, as described above with reference to FIG. 12. The style parametercan indicate whether the vibration force is uni-directional orbi-directional. In addition, a duty cycle parameter can be provided inalternate embodiments indicating the percentage of a time period thatthe vibration force is applied. Also, a command parameter can beincluded to designate the “shape” or profile of the vibration waveformin the time axis, where one of a predetermined number of shapes can beselected. For example, the force might be specified as a sinusoidalforce, a sawtooth-shaped force, a square waveform force, etc.

[0168] A wobble force paradigm is another overlay force that can becommanded by host computer 12. This force creates a random (or seeminglyrandom to the user), off-balance force sensation on the user object. Forexample, it can simulate an erratic control for a damaged vehicle. Themagnitude, duration, and style command parameters can be similar toparameters for the above host commands. The style parameter might alsospecify a type of wobble force from a predetermined list of differenttypes. The wobble force can be implemented using a variety of methods.For example, a preprogrammed “force profile” stored in memory can beimplemented to cause a force sensation that seems random. Or, anequation can be used to calculate a force based on a sine wave or otherfunction or a random result.

[0169] The jolt force is typically a short, high magnitude force that isoutput on the user object, and can be used, for example, to notify theuser of an event or simulated object in the computer environment. Thejolt force can be used as an overlay force which can be felt in additionto any condition forces in effect. Typical parameters include themagnitude of the force of the jolt, the duration of the jolt, anddirection(s) or degree(s) of freedom in which the jolt is applied, whichcan be specified as an angle or particular degrees of freedom. Themagnitude command parameter preferably specifies the magnitude of thejolt force in addition to (above) any other condition or overlay forcemagnitudes, i.e., the magnitude is a differential magnitude “above” thesteady state forces. Thus, the actual magnitude output by actuators 30may be greater than the jolt force magnitude.

[0170] The button force is not an actual force but may be used as acommand to trigger other forces when an input device 39 is activated bythe user. In many game situations, for example, it may be advantageousto trigger a force as a direct response to pressing a button or otherinput device 39 on the interface apparatus 14 rather than generating theforce from a host command after processing the pressed button on thehost computer 12. The other forces triggered by the pressing of thebutton can be specified as a command parameter in the button command;alternatively, a specific button command can be provided for each typeof force.

[0171] For example, a common force to use in conjunction with a buttoncommand is the jolt force. A specific command, e.g., BUTTON_JOLT, can beprovided to cause a jolt force whenever a specified button is pressed,and which includes button and jolt command parameters. Alternatively, abutton command with a JOLT command parameter may be implemented. Whenthe button jolt command is received by microprocessor 26, themicroprocessor can run a button check as a background process untilcommanded to terminate the button background process. Thus, when themicroprocessor 26 determines that the user has pressed a button from thesensor data, the jolt force can be overlaid on any existing forces thatare output.

[0172] The button command sets up the microprocessor 26 to output aforce when the other input device 39 has been activated. The buttoncommand may accept a number of command parameters including, forexample, button and autofire frequency parameters (in addition to anycommand parameters specific to the desired force to be output when thebutton is pressed). The button parameter selects the particularbutton(s) which the microprocessor 26 will check to be activated by theuser and which will provide the desired forces. For example, a joystickmay have multiple buttons, and the software developer may want toprovide a force only when a particular one of those buttons is pressed.A duration parameter can determine how long the jolt lasts after thebutton is pressed. The “autofire” frequency parameter designates thefrequency of a repeating force when the user holds down a button. Forexample, if the user holds down a particular button, the microprocessorcan automatically repeat a jolt force after a predetermined timeinterval has passed after the user first pressed the button. Theautofire parameter can also optionally designate whether the autofirefeature is being used for a particular button and the desired timeinterval before the repeating forces are applied.

[0173] Other rate control commands not shown in the table of FIG. 9 canalso be implemented. For example, if actuators 30 are passive actuators,a “ratchet” force can be provided by sending a ratchet command andappropriate command parameters. This command can simulate an obstructionwhich causes, for example, a user-controlled vehicle to strain in agiven degree of freedom. Thus, a force may be applied when the usermoves the joystick in one direction, then no force is applied when theuser moves the joystick in the opposite direction, and force is againapplied when the joystick is moved in the original direction. Thissimulates an obstruction force at any retraction point, like a ratchet.The style parameters for such a command can indicate a fixed obstructionor a ratchet-style obstruction.

[0174] This concludes the description of rate control commands and forcemodels.

[0175]FIG. 14 is a table 332 showing a number of preferred positioncontrol host commands that can be used in the embodiment of FIG. 5.Herein, “position control” refers to a mapping of a user object in whichdisplacement of the joystick handle or other user object directlydictates displacement of a computer-simulated entity or object. Themapping can have an arbitrary scale factor or even be non-linear, butthe fundamental relation between user object displacements and computerobject or entity displacements should be present. Under a positioncontrol mapping, the computer-controlled entity does not move unless theuser object is in motion; a static user object dictates static commandsto microprocessor 26 from host computer 12.

[0176] Position control is not a popular mapping for traditionalcomputer games, but may be used in other applications such as medicalprocedure simulations or graphical user interfaces. Position control isan intuitive and effective metaphor for force feedback interactionsbecause it is a direct physical mapping rather than an abstract controlparadigm. In other words, because the user object experiences the samephysical manipulations as the entity being controlled within thecomputer, position control allows physical computer simulations to bedirectly reflected as realistic force feedback sensations. Examples ofposition control in computer environments might be controlling a paddlein a pong-style tennis game or controlling a cursor in a windows desktopenvironment.

[0177] Contrasted with rate control's vehicle-centric forces, positioncontrol force feedback roughly corresponds to forces which would beperceived directly by the user. These are “user-centric” forces. Forexample, a paddle displayed on display screen 20 and directly controlledby a user might move through simulated thick mud. Via the force feedbackinterface device 14, the user would perceive the varying forceassociated with movement through a viscous solution. Corresponding tothe realistic physical situation, the force varies with the speed ofmotion of the joystick (and displayed paddle) and orientation of thepaddle face.

[0178] Descriptions will now be provided for several types of positioncontrol forces 334, as referenced in table 332, that can be implementedby microprocessor 26 from host commands. These forces include: vector,groove, divot, texture, barrier, field, paddle, and button reflex jolt.Many of the examples 336 of host commands corresponding to these forcesuse magnitude and style parameters as discussed with reference to therate control paradigms. As with the rate control commands, commandparameters of the same name generally have the same properties fordifferent host commands. However, the duration parameter is typicallynot used for position control commands as much as for rate controlcommands, since the duration of the position control forces aretypically applied depending on the current position of the user object.The position control force models thus generally remain in effect untilthe host computer 12 issues a new host force command or a clear command.In alternate embodiments, a duration parameter can be used.

[0179] Preferred parametrizations for described position controlcommands are summarized in FIG. 14. All the forces listed below caninclude additional command parameters, such as deadband parameters, orincorporate other properties into the parameters listed in FIG. 14.Similar to the host commands shown in FIG. 9, host commands 336preferably include a command portion 338 and a number of commandparameters 340. Commands 336 indicate the type of force which the hostcomputer 12 is instructing the processor 26 to implement. This commandportion may have a corresponding reflex process which the processor 26can retrieve from memory 27 and implement. Command portions 338 can bespecified in virtually any form in other embodiments.

[0180] A vector force is a general force having a magnitude anddirection. Refer to FIG. 12 for a polar representation of the vectorforce. Most position control sensations will be generated by theprogrammer/developer using a vector force command and appropriateinstructions and programming constructs. A duration parameter istypically not needed since the host 12 or microprocessor 26 canterminate or modify the force based on user object motions, not time.

[0181]FIG. 15 is a graph 342 showing a force versus displacementrelationship for a groove force of the present invention. The grooveforce provides a linear detent sensation along a given degree offreedom, shown by ramps 344. The user object feels like it is capturedin a “groove” where there is a restoring force along the degree offreedom to keep the stick in the groove. This restoring force groove iscentered about a center groove position C located at the currentlocation of the user object when the host command was received.Alternatively, the location of the center groove position can bespecified from a command parameter along one or more degrees of freedom.Thus, if the user attempts to move the user object out of the groove, aresisting force is applied.

[0182] The magnitude (stiffness) parameter specifies the amount of forceor resistance applied. Optionally, a “snap-out” feature can beimplemented within the groove reflex process where the groove forcesturn off when the user object deviates from the groove by a givensnap-out distance, shown as distance S. Thus, the microprocessor 26would receive a groove command having a snap distance magnitude. Whenthe microprocessor detects the user object moving outside this snapdistance, it turns off the groove forces. This snap-out feature can beimplemented equally well by the host computer 12 sending a clear commandto turn off forces. Also, a deadband DB can also be provided to allowthe user object to move freely near the center groove position C,specified with a deadband command parameter. A style command parameterindicates the orientation of the groove along one or more degrees offreedom (e.g., horizontal, vertical, diagonal). For example, horizontaland vertical grooves can be useful to provide forces for scroll bars inwindows. A user moving a cursor in a graphical user interface can feelgroove forces moving the cursor and user object toward the middle of thescroll bar. The deadband gives the user room to move the cursor withinthe scroll bar region. The snap-out distance can be used to free thecursor/user object from forces once the cursor is moved out of thescroll bar region.

[0183] A divot is essentially two (or more) orthogonal grooves thatprovide restoring forces in more than one degree of freedom. Thisprovides the sensation of a point detent along a given degree offreedom. If the divot is provided in two degrees of freedom, forexample, then the user object feels as it if has been captured in acircular depression. The user object is captured at a point where thereis a restoring force along both axes to keep the user object at thepoint. The snap-out feature of the, groove force can also be implementedfor the divot. In addition, the deadband feature of the groove can beprovided for the divot command.

[0184] A texture force simulates a surface property, as described abovewith reference to FIG. 4. A texture is a spatially varying force (asopposed to vibration, a time varying force) that simulates the forcefelt, for example, when a stick is moved over a grating. Other types oftextures can also be simulated. The user object has to be moved to feelthe texture forces, i.e., each “bump” of the grating has a specificposition in the degree of freedom. The texture force has severalcharacteristics that can be specified by a programmer/developer usingthe host command and command parameters. These command parameterspreferably include a magnitude, a grit, and a style. The magnitudespecifies the amount of force applied to the user object at each “bump”of the grating. The grit is basically the spacing between each of thegrating bumps. The style command parameter can specify an orientation ofthe texture. For example, the style can specify a horizontal grating, avertical grating, or a diagonal grating (or a superposition of thesegratings). Furthermore, the style parameter can specify if the textureis felt bi-directionally or uni-directionally along a degree of freedom.Alternatively, additional command parameters can be provided to controlthe position of the “bumps” of the texture force. For example,information can be included to instruct the distance between bumps tovary exponentially over a distance, or vary according to a specifiedformula. Alternatively, the texture spacing could vary randomly. In yetother embodiments, the command parameters can specify one of severalavailable standard texture patterns that microprocessor 26 can retrievefrom memory.

[0185] A barrier force, when commanded, simulates a wall or otherobstruction placed at a location in user object space, and is describedabove with reference to FIG. 4. The host command can specify thehardness of the barrier (magnitude of the force applied), the locationof the barrier along the degree of freedom, and the snap distance orthickness of the barrier. Horizontal barriers and vertical barriers canbe provided as separate host commands, if desired. As indicated in graph346 of FIG. 16, a barrier force only has a finite thickness. The forceincreases steeply as the user object is moved closer into the barrier(past point B). The snap-through distance defines the size of the regionwhere the barrier is felt by the user. If the user object is moved intoa barrier, and then is moved past the thickness of the barrier, thebarrier force is turned off. The barrier force can act as a hardobstruction, where the microprocessor provides maximum force magnitudeto the user object 34, or as a bump or softer barrier, where a smallerforce magnitude is applied (as specified by the magnitude commandparameter). The barrier can remain for an extended period unless removedor moved to a new location. Multiple barriers can also be provided insuccession along a degree of freedom.

[0186] Alternatively, the barrier force can be provided by sending ahost command having only two command parameters, hardness and location.The hardness parameter can specify the height and slope of the resistiveforce. As shown in graph 348 of FIG. 16, the user object can move fromleft to right along the distance axis. The user object feels a resistiveforce when hitting the barrier at point B. After the user object hasbeen moved to point S (the snap-distance), the force is applied to theuser object in the opposite direction (a negative magnitude force),which decreases as the user object is moved in the same direction. Thissimulates a bump or hill, where the force is resistive until the userobject is moved to the top of the bump, where the force becomes anassisting force as the object is moved down the other side of the bump.

[0187] A force field type force attracts or repulses the user objectwith respect to a specific position. This force can be defined bycommand parameters such as a field magnitude and the specific fieldorigin position which the force field is applied with respect to. Asense parameter can be included to indicate an attractive field or arepulsive field. For example, the force field can be an attractive fieldto simulate a force of gravity between the field origin position and auser-controlled cursor or graphical object. Although the field originposition can be thought of as a gravitational mass or an electriccharge, the attractive force need not depend on the inverse square ofdisplacement from the specific position; for example, the force candepend on an inverse of the displacement. The attractive force fieldalso attempts to maintain the user object at the field origin positiononce the user object has been moved to that position. A repulsive fieldoperates similarly except forces the user object away from a specifiedfield origin position. In addition, ranges can be specified asadditional command parameters to limit the effect of a force field to aparticular distance range about the field origin position.

[0188]FIGS. 17a-17 i are diagrammatic illustrations of a “paddle”computer object 350 interacting with a “ball” computer object or similarobject 352. These computer objects can be displayed on display screen 20by host computer 16. The force interactions between the ball and paddlecan be controlled by a software developer using a host command, asexplained below. In the described example, paddle object 350 iscontrolled by a player by a position control paradigm such that themovement of paddle object 350 is directly mapped to movement of userobject 34. In alternate embodiments, ball object 352 or both objects canbe controlled by players.

[0189]FIGS. 17a-17 h show how paddle object 350 interacts with a movingball object 352 as ball object 352 collides with the paddle object. InFIG. 17a, ball 352 first impacts paddle 350. Preferably, an initialforce is applied to user object 34 in the appropriate direction. InFIGS. 17b and 17 c, ball 352 is moving into the compliant paddle or“sling”. Preferably, a simulated mass of ball 352 is felt by the userthrough user object 34 which is appropriate to the simulated velocity ofthe ball, the simulated compliance of the paddle, and thestrength/direction of simulated gravity. These parameters can preferablybe set using a host command with the appropriate parameters. Forexample, the following host command can be used:

PADDLE (B_mass, B_vel_x, B_vel_y, Gravity, Sense, Compliance_X,Compliance_Y)

[0190] where the command parameter B_mass indicates the simulated massof the ball, B_vel_x and B_vel_y are the velocity of the ball, gravityis the strength of gravity, sense is the direction of gravity, andCompliance_X and Compliance_Y are the simulated compliance or stiffnessof the paddle object 34. Other parameters can also be included tocontrol other physical aspects of the computer environment andinteraction of objects.

[0191] In FIG. 17d, the ball has reached a maximum flexibility point ofpaddle 34 and can no longer move in the same direction. As shown inFIGS. 17e through 17 g, the ball is forced in the opposite direction dueto the compliance of the paddle. In addition, the user may preferablyexert force on user object 34 to direct the ball in a certain directionand to add more velocity to the ball's movement. This allows the user afine degree of control and allows a significant application of skill indirecting the ball in a desired direction. The force feedback paddle isthus an improved component of “pong” type and other similar video games.In addition, the paddle 350 can optionally flex in the oppositedirection as shown in FIG. 17h.

[0192] A schematic model of the forces interacting between ball 352 andpaddle 350 is shown in FIG. 17i. A spring force indicated by springconstant K is provided in both degrees of freedom X and Y to indicatethe springiness of the paddle 350; g is a gravity direction. Inaddition, a damping force indicated by damping constant B is alsoprovided to slow the ball 352 down once it contacts paddle 350. Thespring and damping forces can also be applied in one degree of freedom.

[0193] The paddle control algorithm is a dynamic algorithm in whichmicroprocessor 26 computes interaction forces while a ball compressesthe paddle and then releases from the paddle. The paddle command is sentby host computer 12 when the ball contacts the paddle. The paddlecommand reports ball location to the host computer so that the host canupdate graphics displayed on display screen 20 during the interactionperiod. In presently preferred embodiments, the updates only need to beprovided at about 60 Hz to the host, since most displays 20 can onlydisplay at that rate. However, the forces should be computed and outputat about 500 Hz or more to provide a realistic “feel” to theinteraction. Thus the local microprocessor can compute the forcesquickly while occasionally reporting the sensor readings of the paddleto the host at a slower rate. Other types of video game or simulationinteractions can also be commanded with a high-level host command in asimilar fashion. This concludes the description of position controlparadigms.

[0194] In addition, a clear command is preferably available to the hostcomputer. This command can include a parameter specifying particulardegrees of freedom and allows the host computer to cancel all forces inthe specified degrees of freedom. This allows forces to be removedbefore other forces are applied if the programmer does not wish tosuperimpose the forces.

[0195] Also, a configuration host command can be provided. This commandcan initially set up the interface device 14 to receive particularcommunication parameters and to specify which input and output will beused for a particular application, e.g. the host computer can instructlocal microprocessor 26 to report specific information to the hostcomputer and how often to report the information. For example, hostcomputer 12 can instruct microprocessor 26 to report position valuesfrom particular degrees of freedom, button states from particularbuttons of interface device 14, and to what degree to report errors thatoccur to the host computer. A “request information” command can also besent by host computer 12 to interface device 14 to receive informationstored on the interface device 14 at the time of manufacture, such asserial number, model number, style information, calibration parametersand information, resolution of sensor data, resolution of force control,range of motion along provided degrees of freedom, etc. This informationmay be necessary to the host computer so that the commands it outputs tothe local processor 26 can be adjusted and customized to the particulartype of interface device 14. If the USB communication interface is used,other information necessary to that interface can be provided to thehost upon a request command, such as vendor identification, deviceclass, and power management information.

[0196] In addition, the above described forces can be superimposed. Thehost computer can send a new host command while a previous host commandis still in effect. This allows forces applied to the user object to becombined from different controlling commands. The microprocessor 26 orhost computer may prevent certain commands that have contradictoryeffects from being superimposed (such as a restoring force and arestoring spring). For example, the latest host command sent canoverride previous commands if those previous commands conflict with thenew command. Or, the conflicting commands can be assigned priorities andthe command with the highest priority overrides the other conflictingcommands.

[0197] It should be noted that the high-level host commands and commandparameters described above are merely examples for implementing theforces of the present invention. For example, command parameters thatare described separately can be combined into single parameters havingdifferent portions. Also, the distinct commands shown can be combined orseparated in different ways, as shown above with the example of thecondition command for providing multiple rate control condition forces.

[0198] In addition to common interface devices with one or tworectangular or spherical degrees of freedom, such as standard joysticks,other interface devices can be provided with three or more degrees offreedom. When the third degree of freedom is about an axis along thestick itself, those skilled in the art call it “spin” or “twist.” Eachdegree of freedom of a user object can have its own dedicated high-levelhost command. By independently associating high-level host commands toeach degree of freedom, many possible combinations of position control,rate control, and other abstract mappings can be implemented withinterface devices.

[0199] For example, for a common joystick with two degrees of freedom, acomputer game might allow the joystick to control flight of aspacecraft. Forward-backward motion of the joystick handle mightimplement thrust control to dictate an acceleration of the spacecraft.Left-right motion of the joystick might implement direction control todictate an angular velocity of the spacecraft's trajectory. Thisparticular thrust-direction paradigm is particularly popular in currentgames, but there are many variations. For example, in a flightsimulator, the forward-backward motion of the joystick might control thepitch of an aircraft while the left-right motion might control roll ofthe aircraft. In a driving game, the forward-backward motion of thestick might be a rate control mapping to an acceleration of the car,while the left-right motion might be a position control mapping to alocation of the car across a span of road.

[0200] Multiple control paradigms may also be mixed in a single degreeof freedom. For example, a joystick may have position control for smalldeviations from the origin in a degree of freedom and rate control forlarge deviations from the origin in the same degree of freedom. Such amixed control paradigm can be referred to as a local position/globalrate control paradigm.

[0201]FIG. 18 is a block diagram illustrating an example of a functionalmicroprocessor 26 implementation 380 of the present invention forprocessing the host commands and command parameters to output forces touser object 34. Implementation 380 is preferably provided on themicroprocessor 26 using instructions stored in memory 27. The use ofprogram instructions to perform operations on a microprocessor is wellknown to those skilled in the art, and can be stored on a “computerreadable medium.” Herein, such a medium includes by way of examplememory 27 such as RAM and ROM, magnetic disks, magnetic tape, opticallyreadable media such as CD ROMs, semiconductor memory such as PCMCIAcards, etc. In each case, the medium may take the form of a portableitem such as a small disk, diskette, cassette, etc., or it may take theform of a relatively larger or immobile item such as a hard disk drive.Preferably, various subprocesses 382, 384, 386, 387, and 388 run inparallel on microprocessor 26 to optimize responsiveness of the forcefeedback interface device 14. These processes are also referred to as“processors” herein. Various parameters and data are shared by thesubprocesses of implementation 380 in a preferred embodiment.

[0202] Throughout the following discussion of implementation 380,parameter sets or parameter pages can be stored to speed computation andapplication of forces. Herein, parameter sets will be consideredsynonymous with parameter pages. Rather than reading, storing andapplying host commands and command parameters (and/or other parameters)as soon as the command is received, all or some of the commands andparameters defining a force environment may be stored and grouped intoparameter pages stored in memory 27. This force environment can describeparticular forces that may be quickly read from the parameter page. Whenthe appropriate force environment is required by the host computer, themicroprocessor can retrieve the parameter page from memory. As with pageswapping in video display systems, implementation 380 could then useactive pages for a current force environment and “hidden” pages forcommand/parameter sets under construction. In addition, preset orpredefined force environments can be retrieved, which are standardizedforce environments that are provided with interface device 14 or whichcan be loaded onto interface device 14 from the host computer. In thepreferred embodiment, a stored parameter page would include forceparameters and reporting parameters, which are internal microprocessorparameters that are derived from the host command and command parametersand which are discussed below.

[0203] Host communication and background process 382 maintainscommunication between the microprocessor 26 and the host computer 12.Host communication and background process 382 receives high-level hostcommands and command parameters from the host 12 and sends this data toa command process 384. Process 382 also receives sensor data from areporting process 387 described below. Process 382 directly relaysinformation received from process 387 to the host 12. Essentially,process 382 acts as a communication “switchboard” between themicroprocessor 26 and the host computer 12. Preferably, process 382 (orprocess 384) manages an input buffer on microprocessor 26 which is usedto buffer incoming commands and data from host computer 12. The inputbuffer is especially useful in embodiments including the USB interfaceand other interfaces with high communication rates.

[0204] The command process 384 processes incoming high-level hostcommands and command parameters from the host 12 and transmitted via thehost communication and background process 382. Based on the incomingcommands, the command process 384 sets reporting parameters and forcefeedback control parameters. These types of parameters are internalparameters of microprocessor 26 and are to be distinguished from thecommand parameters 308 included in a high-level host command sent by thehost. The internal parameters are derived from the command parametersand may, in some instances, be identical to the command parameters, asexplained below.

[0205] The reporting parameters are internal parameters that specify tothe microprocessor 26 which particular data and at what rate to reportto host computer 12. The reporting parameters can, for example, specifywhether to report positions or velocities of user object 34 forparticular degrees of freedom, a communication speed, or whether and inwhat way errors are reported. The reporting parameters are derived fromthe configuration commands received from the host computer 12 and areprovided to the status update process 386 and reporting process 387 sothat process 387 knows which information to report to the host computer12 via the host communication and background process 382.

[0206] Force feedback control parameters (“force parameters”) areinternal parameters that are provided or updated by command process 384and are used by force algorithm computation and actuator control process388. The force parameters are derived from the command parameters 308included in the received host command. Command process 384 examines thecommand parameters and updates the internal force parameters so that theother processes 388 and 386 can access the most recent force parameters.This process of providing/updating force parameters implemented byprocess 384 is described below with reference to FIG. 19.

[0207] The status update process 386 receives reporting parameters fromthe command process 384. Based on the parameters received, process 386reads sensors 28 and clock 29 and stores sensor reading histories andtiming histories. Process 386 also can compute values, such as velocityor acceleration values, derived from sensor position data, the sensordata histories, timing data, or combinations of this data. Herein, theterm “sensor data” refers to both data received directly from thesensors (sensor readings) and/or values derived from the sensorreadings, including histories of sensor data. “Timing data” or “timedata” refers to specific values representing a period of time, includinghistories of timing data. Periodically, reporting process 387 reads dataprovided and stored by process 386 (or process 386 could send the datato process 387 directly). The sensor and timing data is also “sent” to aforce algorithm computation and actuator control process 388. The term“sent” or “received” herein refers to one process providing data thatanother process eventually receives. The actual implementation to sendand receive data between processes can vary in different embodiments.For example, the sending process may store computed data in memory andthe receiving process can retrieve the data from memory at its own rate.

[0208] Reporting process 387 receives sensor data from status updateprocess 386 and reports this data to host computer 12 at appropriatetimes or upon receiving a request from the host 12 through backgroundprocess 382. Reporting parameters are sent to process 387 by commandprocess 384. In addition, general status and error information may besent to reporting process 387 from force computation process 388. Theprocess implemented by reporting process 387 is described in greaterdetail with respect to FIG. 21. In alternate embodiments, reportingprocess 387 can be merged with background process 382, for example, ifreporting data to the host at a regular rate (in “stream” mode).

[0209] Force algorithm computation and actuator control process 388 usesforce parameters and sensor data from the command process 384 and thestatus update process 386 to compute forces to be applied to user object34. The force parameters are derived from command parameters thatcharacterize various force models, as described in detail above. Process388 computes a resultant force to be applied to actuators 30 bycombining effects of all force models in effect.

[0210] It should be emphasized that the processes 382, 384, 386, 387,and 388 within the implementation 380 in FIG. 18 preferably run inparallel on the microprocessor 26, e.g., using a multi-taskingenvironment. Running all these processes sequentially would dramaticallyslow the force feedback response to user manipulation of the user object34.

[0211] The implementation 380 shown in FIG. 18 is intended as an exampleof a way to divide the various subprocesses of microprocessor 26 intological divisions. In other embodiments, various other implementationscan be provided to join or separate some or all of the describedfunctions of microprocessor 26.

[0212]FIG. 19 is a flow diagram illustrating command process 382 of FIG.18 in greater detail beginning at 390. Initially, the host computer willestablish a communication link with interface device 14 in step 391.This can be accomplished by sending a predetermined signal orinformation which the interface device is waiting to receive. Theinterface device then can send an answer signal indicating it is readyto receive commands. If the USB communication interface is being used,the command process 382 preferably requests a USB address from the host,which the processor 382 then receives and stores. Whenever a data packetis then sent from the host, the command processor 384 can check theaddress of the data packet and compare it to the stored address todetermine if the packet is meant for the microprocessor 26.

[0213] In addition, if USB is being implemented, the command processor384 can check for data in the USB communication protocol and reportingprocessor 387 can send out data in this protocol. This protocol includesa token packet, followed by a data packet, which is followed by ahandshake packet, as is well known to those skilled in the art. The hostcommands can be encrypted in the data packets.

[0214] In next, step 392, host computer 12 may require thecharacteristics of the interface device 14 so that appropriate forcefeedback commands suited to the particular interface device can beprovided by the host computer. These characteristics may include, forexample, the serial number, model number, style, number of provideddegrees of freedom of user object 34, calibration parameters, andreporting rate of the interface device. Upon receiving a request forsuch information from the host computer 12, such as a “requestinformation” command, the microprocessor 26 sends the information to thehost computer 12 in step 392. The host computer would normally requestthese characteristics only at power-up or at the start of force feedbackimplementation.

[0215] In next step 394, the microprocessor 26 receives configurationcommands from the host computer 12 and sets appropriate reportingparameters. As mentioned above, the reporting parameters may determinewhether such information as sensor data, which includes sensor readings,values computed from sensor readings, and/or sensor “histories” (i.e., anumber of previously recorded or computed sensor values), or clock timevalues are sent to the host computer 12 from the status update process386. The sensor data may include sensor error data, histories of datadescribing which buttons have been pressed on the interface device,positions, velocities, and/or accelerations of the user object, datafrom which degrees of freedom will be reported to the host computer, andwhether data is reported to the host computer in a query or stream mode.These configuration options allow the programmer to set up which datathe host computer will receive from the local microprocessor. Forexample, if an application requires user object position data in onlyone of two provided degrees of freedom, then it is a waste of processingtime for the microprocessor to be sending information of the unuseddegree of freedom to the host computer. The programmer can set reportingparameters with configuration commands to send only the necessary datato the host computer.

[0216] In next step 396, the process checks if a host command has beenreceived. If not, step 396 loops continuously until a host command isreceived. Step 398 is then implemented, in which the process determineswhether the received command(s) is a configuration command. Aconfiguration command sets the reporting parameters, as described above.If the command is a configuration command, step 400 sets appropriatereporting parameters and/or resets the reporting parameters to provide anew configuration during the operation of the interface device. If step398 determines that the received command is not a configuration command,then step 398 has detected a force command which controls force feedbackfunctionality of the interface device 14. Force commands include thosehost commands that provide command parameters that affect the internalforce parameters (e.g., the host commands shown in FIGS. 9 and 14).

[0217] In step 402, the force commands and command parameters set forceparameters, such as those related to implementing a particular forceparadigm or model specified by the force command. Process 388 accessesthese force parameters in memory to apply forces using actuators 30, asdescribed with reference to FIG. 22. As an example, the force commandand force parameters may designate particular buttons on the interfacedevice 14 and assign a jolt force model to each designated button. If auser then presses a designated button, the jolt assigned to the pressedbutton would in turn be activated using whatever force parameters arecurrently in memory. An example of force parameters is described belowwith reference to FIG. 23. After setting the force parameters, step 402then transfers control back to step 396 to wait to receive another hostcommand.

[0218] In addition, in the preferred embodiment, process 384 also isregularly checking/receiving for a “heartbeat” signal from host computer12 after a predetermined time interval. This signal would be a safetycheck to indicate that the host computer is still connected to interfacedevice 14 and that the host has an “OK” status. If no heartbeat signalis received within the time interval, the interface device 14 candeactivate and wait for an initialization command from the host. The“heartbeat” signal can be a normal signal or host command, or it can bea signal specifically used as a heartbeat signal that the host computercan send if no other signals have been sent within the time interval.After a signal has been received in step 396, process 384 preferablystores the time that the signal was received in a particular memorylocation. Process 388 can examine this time to determine if the intervalhas been exceeded (described below).

[0219]FIG. 20 is a flow diagram illustrating status update process 386of FIG. 18, beginning at a step 410. In step 412, the process 386examines reporting and force parameters set by the command process 384.Preferably, process 386 examines the reporting and state parameters inmemory 17 which have been updated by command process 384. From both thereporting and force parameters, step 414 determines which sensors willbe read. The force parameters determine which sensor data is necessaryfor the process 388 to compute a force. For example, if the forceparameters determine that a force needs to be calculated about thex-axis and not the y-axis, then the sensor data from the y-axis sensorsis not needed to computer forces. The reporting parameters determinedwhich sensor data to report to the host computer. Thus, the reportingparameters may also specify that y-axis sensor data does not have to besent to the host computer, since the host computer is ignoring thatparticular data. Thus, since the y-axis data is both not being used tocompute a force and is not needed by host 12, the microprocessor 26determines in step 414 not to read the y-axis sensors.

[0220] Step 416 determines whether velocity and/or acceleration arealways computed. The result is of this step depends on the particularembodiment that is implemented. In some embodiments, it may be simplerand require less processing time if velocity and/or acceleration dataare always computed, regardless of whether the velocity/accelerationdata is needed to compute forces or to be sent to host 12. In otherembodiments, the velocity/acceleration data can be computed only if suchdata is necessary to compute force values or if the host 12 requiresthese values. In yet other embodiments, the mode (“always compute” or“compute only when necessary”) can be set depending on the particularapplication or other determining factor.

[0221] In an embodiment that always computes velocity and acceleration,step 418 is implemented, in which the velocity and/or accelerationvalues are computed using sensor readings and timing data. For example,a history of recorded position values and associated time intervals canbe used to calculate velocity. The process then continues to step 422.If such an embodiment is not being used, then step 420 computes thevelocity and/or acceleration values only if appropriate. The process 386can examine the force parameters and reporting parameters, similarly asin step 414, to determine if velocity and/or acceleration values shouldbe computed.

[0222] After step 418 or 420, step 422 is performed, in which theprocess 386 stores in memory 27 the sensor data and timing data readfrom sensors 28, clock 29, and computed in step 418 or 420. The sensordata and timing data may also include data pertaining to other inputdevices 39, e.g., if a button has been pressed (sensor data) and howlong a button on the interface device 14 has been pressed (timing data)so that a button repeat or button hold (“autofire”) feature may beactivated at the proper time. As noted above, process 386 is preferablysharing the microprocessor's 26 processing time since multiple processesare running in parallel (multi-tasking). In this case, the process 386may need to wait at step 424 until the microprocessor 26 is available orto purposely allow another waiting process to use microprocessor 26. Inaddition, the waiting step may be necessary to write output data tomemory 27 at a consistent or slower time to allow force computationprocess 388 greater flexibility in reading the output data from thememory.

[0223]FIG. 21 is a flow diagram illustrating reporting process 387 ofFIG. 18 to report data to the host computer, beginning at a step 430.Step 432 determines whether reporting is done in query or stream mode asspecified by the reporting parameters set by command process 384. Inthis discussion, query mode uses an asynchronous reporting method basedon requests for information from the host computer, and stream mode usesa synchronous reporting method based on predetermined time intervals.

[0224] In query reporting mode, step 434 determines whether a requestfor a report has been received from host computer 12. The request can bereceived directly by reporting process 387, or, alternatively, therequest can be relayed to reporting process 387 through command process384. When the request is received, step 436 reports (i.e., sends out)sensor data and timing data stored in step 422 in FIG. 20 and errorinformation and force values from process 388 to the host. Theparticular data sent out depends on the reporting parameters specifiedby the configuration commands and the request received from the host.For example, in some embodiments, the host 12 may be able to requestparticular information. The process then returns to step 432 todetermine if query or stream mode is being used. Thus, in the describedembodiment, modes can be switched at any time during data transmission.In alternate embodiments, one particular reporting mode may be the onlyoption available. Alternatively, both modes may be available, but onceone mode is selected at the beginning of the operation of interfacedevice 14, that mode may not be switched.

[0225] In stream reporting mode, step 438 determines whether thereporting time period has expired. Preferably, a standard reporting timeperiod is set when the interface device and host computer 12 are firstset up. When the time period has expired, step 440 reports data storedin step 422 in FIG. 20 in accordance with the reporting parameters. Iftime has not expired, the process returns to step 432 to again determinethe reporting mode.

[0226]FIG. 22 is a flow diagram illustrating force algorithm computationand actuator control process 388 of FIG. 18 beginning at a step 450.Preferably, all forces in each degree of freedom are initialized to zerobefore step 450 at power up or upon receipt of a clear command from thehost computer 12. Thereafter, process 388 would begin at 450 and proceedwith step 452. In step 452, an axis or degree of freedom for which aforce is to be applied is selected. Herein, “axis” is synonymous with adegree of freedom provided by the interface device 14. If two axesrequire forces to be applied, an axis that has not had a force appliedin the current iteration is preferably selected in step 452. Forexample, if forces are required about the x and y axes, and if the forceon the x axis was just computed and applied in the previous iteration ofthe loop, then the y-axis is preferably selected. In addition, a totalforce in the selected axis is initialized to zero in step 452.

[0227] Step 456 computes a force in the selected axis according to thenext reflex process selected in accordance with the force parameters.This step preferably includes selecting an appropriate reflex process,retrieving the necessary sensor data, timing data, and other data, andcomputing a force value using the selected reflex process and retrieveddata. The reflex process is selected by examining the force parameters.The current values of the force parameters reflect the host commandsthat are currently in effect. Since multiple host commands (reflexprocesses) may simultaneously be in effect, the force parameters areexamined by process 388 to determine one of the reflex processes toexecute to compute a force. Thus, process 388 can examine the forceparameters to determine which commands were sent by host computer, anddetermine which reflex process to execute in accordance with thosecommands. As described above with reference to FIG. 5, the reflexprocess can include process steps, equations, force profiles, or othercombinations of instructions to compute a force from sensor data, timingdata, command parameters, other input data from input devices 39, and/orother related information. The command parameters are reflected in theforce parameter values. Process 388 thus retrieves the necessary sensordata, timing data, force parameters and/or other data required by theselected reflex process to compute a force value.

[0228] In step 458, process 388 adds the force value computed in step456 to the total force for the axis initialized in step 452. Inalternate embodiments, process 388 may limit the total force value or aportion of the total force value computed in step 458. For example, ifprocess 388 is keeping track of which force values are condition forcesand which force values are overlay forces, the process 388 can limit thesum total of condition forces to a predetermined percentage of maximumactuator force output, such as 70% of maximum output. This allows someof the available force range to be used for overlay forces, such asbutton jolts, vibrations, etc. that may applied on top of the conditionforces. This limiting is preferably performed after all condition forcesthat are in effect have been computed, so that overlay forces can beapplied over the sum of all condition forces. Other forces can belimited in alternate embodiments.

[0229] In next step 460, process 388 determines if another reflexprocess needs to be executed for the currently selected axis. This wouldbe true if additional host commands are in effect for which forces havenot yet been computed and added to the total force. If so, the processreturns to step 456 to check the force parameters, execute anotherreflex process to compute a force, and add that force to the totalforce. If, in step 460, there are no more reflex processes to beexecuted for the selected axis, then total force represents all forcesin effect on the selected axis. Total force for the selected axis isthen stored in memory 27 in step 462.

[0230] In step 464, process 388 determines whether another axis (degreeof freedom) needs to have a total force value computed. If so, steps452, 456, 458, 460, and 462 are repeated for other axes until the totalforces for the other axes are computed and stored.

[0231] If step 464 determines that there are no more axes (degrees offreedom) for which forces need to be computed, step 466 may limit thetotal force on each axis. Since the total force on an axis computedabove may exceed hardware specifications of the interface device, suchas actuator force output, step 466 sets the total force to lie withinthe hardware's design range. Step 466 also may modify the total forcecomputed above when it may be unsafe to the user as indicated by anerror flag. For instance, in the preferred embodiment, an error flag maybe set if a safety condition is violated, as described in steps 468-472below. This causes the output force to be zero. In the preferredembodiment, the process 388 applies a smoothly increasing force to userobject 34 after such a safety condition, since an abrupt jump in forceoutput at the level before the safety condition might be dangerous forthe user. In step 466, the process 388 can check how long ago the errorflag was set by examining error timing information, and can limit thetotal force in accordance with a smooth ramp function of increasingforce.

[0232] Next step 468 applies safety conditions to the total force oneach axis resulting from step 466. Safety conditions may be violatedwhen, for example, safety switch 41 as shown in FIG. 1 is activated, orwhen a specific command is sent by the host computer 12. When the safetyconditions are violated, forces on the actuators 30 are sent to zero instep 470. The error flag is then set in step 472 indicating theviolation and timing information is written as to when the erroroccurred. Process 388 then waits in step 474 until the microprocessor 26is once again ready to proceed, similar to step 424 of FIG. 20.

[0233] As an additional safety feature, process 388 preferably examinesmemory 27 to determine if the host's “heartbeat” signal has beenreceived within the required time interval. If process 388 determinesthat the last signal was received outside of the allowed interval, thenprocess 388 assumes that the host has been disconnected or has had anerror. All power to actuators 30 is thus turned off as a safety measureuntil an appropriate initializing command is received from the host.

[0234] If the safety conditions are not violated in step 468, the totalforce for each axis is signaled to the appropriate actuators 30 to applycorresponding forces on those axes of the user object 34. In addition,process 388 can send any error information and any force values thathave been output to reporting process 387, which determines whether tosend the data to the host as described above (error information is sentto process 387 regardless of safety conditions). Preferably, process 388writes this information to memory where reporting processor 387 mayretrieve it. Subsequently, process 388 waits at step 474 until themicroprocessor 26 is ready. After step 474, the process returns to step452 to select another axis in a new iteration of force computation andapplication.

[0235] An illustrative application of the implementation 380 is nowdescribed with reference to FIG. 23. In this example, a sluggish forcewill be applied to the user object 34 by the host computer 12 sending aSLUGGISH host command. A restoring spring force using a SPRING hostcommand will then be commanded. Both the sluggish and restoring springforce models were discussed above under rate control paradigms and arelisted in FIG. 9.

[0236] The force parameters 480 and 482 in FIG. 23 represent locationsin memory 27 used to store the force parameters for the SLUGGISH andSPRING commands. Preferably, a set of locations is similarly allocatedto store force parameters for each command implemented by themicroprocessor 26. The force parameters resulting from each host command484 sent by the host computer 12 is shown. The locations of the sluggishforce parameters are labeled by damping coefficients (B) for velocitycomponents in positive and negative X and Y directions. Similarly, thespring table locations are labeled by spring coefficients (K) in thepositive and negative X and Y axes and deadband sizes in the X and Yaxes.

[0237] Three host commands 484 are illustrated sequentially in FIG. 23:

SLUGGISH(50, X bi)

SLUGGISH(90. X(+) uni)

SPRING( 65 , X bi, 85)

[0238] The two SLUGGISH command parameters 308 are the dampingcoefficient and style. The coefficient is a percentage of a maximumdamping coefficient: 50% and 90%. The style command parameter in thefirst SLUGGISH command indicates a bi-directional force on the X axis.The style parameter in the second SLUGGISH command indicates auni-directional force on the X axis in the positive direction on thataxis.

[0239] The three SPRING force feedback parameters are springcoefficient, style, and deadband. The spring coefficient parameterindicates 65% of a maximum spring coefficient. The style parameterindicates that the force is bi-directional in the X axis. The deadbandis 85% of a maximum deadband size.

[0240] A duration command parameter can also be included for each of thehost commands 484, as shown in FIG. 9, to provide the length of timethat the command will be in effect. In the present example, however, thecommands are assumed to be of infinite duration, and thus no durationcommand parameter is shown. The commands can be cancelled, for example,by a clear command from the host. Alternatively, as shown, the commandscan be cancelled or changed by another command of the same type.

[0241] After the requested interface device information is sent to thehost 12 in step 392 in FIG. 19, the host communication and backgroundprocess 382 receives configuration commands in either step 394 or step398. These configuration commands cause appropriate reporting parametersto be set. These reporting parameters can be implemented, for example,as flags corresponding to each allowed degree of freedom, other inputdevice 39, position/velocity, query/stream mode, etc. to indicatewhether to report data from those devices to the host (and to selectmodes, when appropriate). For maximum efficiency, the reportingparameters would only have flags set for the X axis, since Y-axis datais not necessary. However, the Y-axis sensor data might be needed byhost computer for other reasons, and thus still might have flags set andthus be reported to the host.

[0242] Thereafter, the force parameters 480 and 482 are set in step 402of FIG. 19 based on the SLUGGISH and SPRING host commands and thecommand parameters they include, as shown in FIG. 23. The commandSLUGGISH(50, X bi) causes step 402 to write “50” in the force parameterlocations 486 corresponding to x-axis coefficients B_(X)(+) andB_(X)(−). All the remaining locations of all the other force parametersare zero, since it is assumed that the first sluggish command is thefirst command received by interface device 14 after power up.

[0243] The other processes 386 and 388 examine the force parameters 480and 482 (as well as other force parameters for other reflex processes)and are implemented as shown in FIGS. 20 ad 22. Thus, when state updateprocess 386 determines which sensors to be read in step 414 of FIG. 20,it examines the force parameters 480 and 482 to determine which commandsare in effect. Since all of the restoring force parameters 482 for therestoring spring force are zero, a restoring spring command is not ineffect (processes 386 and 388 only actually need to look at a subset ofthe force parameters to determine if the command is in effect). However,force parameters 480 include two values (“50”), and thus is in effect.Thus, only the x-axis sensors need to be read (assuming the host doesnot need y-axis information, as indicated by the reporting parameters).In step 420 (if implemented), process 386 would calculate velocity fromthe sensor readings (and/or a history of sensor readings) and timingdata, since the sluggish command requires a velocity value to compute aforce (accelerations are irrelevant in the present example).

[0244] Process 388 would check force parameters 480 and 482 in step 456of FIG. 22. The X axis is the only relevant axis to select in step 452.Since force parameters 482 are all zero, process 388 knows not toexecute a restoring spring reflex process. Since force parameters 480 doinclude non-zero values, a sluggish reflex process should be executed.In one example, the reflex process would include the equation F=BV,where B is the coefficient stored at locations 486 a and 486 b, and V isthe velocity calculated by state update process 386. F is the totalforce that would be output by actuators 30 about the axis. Preferably,all the available host commands have force parameters that processes 386and 388 would similarly check to determine which commands are in effect.

[0245] Referring back to FIG. 23, the second command SLUGGISH (90, X+UNI) is sent by host computer 12 after the first sluggish command. Sincethe second SLUGGISH command is uni-directional in the positive x-axis,only the first location 486 a for the B_(X)(+) force parameter has thenew coefficient “90” written over the previous value. The restoringspring force parameters are unchanged by the SLUGGISH commands. One wayto cancel the first SLUGGISH command would be to send a second SLUGGISHcommand having all command parameters equal zero.

[0246] The status update process 386 would operate similarly for thesecond SLUGGISH command as for the first SLUGGISH command. The forcealgorithm computation and actuator control process 388 would operatesimilarly as well, except that the sluggish reflex process selected instep 456 of FIG. 22 would compute a different sluggish force forvelocities in the positive x direction (based on a coefficient of 90)than in the negative x direction (based on a coefficient of 50). Theprocess 388 would use the sensor information from status update process386 to determine which direction the user was moving the user object anduse the appropriate coefficient.

[0247] Referring back to FIG. 23, the third command sent by host 12 isthe SPRING command SPRING (65, X BI, 85). Step 402 of FIG. 19 thuschanges the restoring spring force parameters 482 by writing 65 forK_(X)(+) and K_(X)(−) and 85 for DB_(X). The SLUGGISH force parametersare unaffected by the SPRING command and thus remain in effect with theprevious values. Process 388 would execute the sluggish reflex processand compute a force, then execute the restoring spring reflex processand compute a force. The restoring spring reflex process could be, forexample, implemented by the equation F=kx, where k is the springconstant and x is the position of the user object with respect to theorigin position. The two forces from sluggish and spring reflexprocesses would be added together at step 458. Therefore, the sluggisharid restoring spring force models are superimposed on the user object34 after the SPRING command in FIG. 23. This would create a viscous feelon the user object 34 and simultaneously apply force toward the originposition of the user object.

[0248] More generally, for other command sequences not shown in FIG. 23,any number of force models may be superimposed. For example, two forcescould be superposed if the first SLUGGISH command were immediatelyfollowed by the SPRING command.

[0249] Alternatively, the three commands shown in FIG. 23 can bereceived by microprocessor 26 and all the force parameters shown afterthe SPRING command can be stored as a parameter page in memory to form a“force environment.” When this force environment was desired to beapplied to user object 34, the page of force parameters and reportingparameters would be retrieved and processed by processes 386 and 388.This can be useful when many different commands are desired to beapplied simultaneously: The microprocessor would not apply each hostcommand as it was received, but would load all the desired forceparameters for a force environment at once from memory.

[0250] While this invention has been described in terms of severalpreferred embodiments, it is contemplated that alterations,modifications and permutations thereof will become apparent to thoseskilled in the art upon a reading of the specification and study of thedrawings. For example, many possible types of actuators and sensors canbe used in the present invention. Also, many types of mechanisms can beincluded to provide one or more degrees of freedom to object 34. Inaddition, different types of interfaces can be used to connect the hostcomputer to the local microprocessor. A wide variety and types of forcescan be transmitted to a user object by the present invention. Manydifferent types of force models can be implemented in many distinctprocesses running on the microprocessor, only some of which aredescribed herein. In addition, the application of reflex processes on alocal microprocessor can be implemented in a variety of ways.Furthermore, certain terminology has been used for the purposes ofdescriptive clarity, and not to limit the present invention. It istherefore intended that the following appended claims include all suchalterations, modifications and permutations as fall within the truespirit and scope of the present invention.

What is claimed is:
 1. A system for controlling an electromechanicalinterface apparatus manipulated by a user, the system comprising: a hostcomputer system for receiving an input control signal and for providinga host command having at least one command parameter to control forceson a user manipulable object of said interface apparatus, wherein saidhost computer system updates a process in response to said input controlsignal; a processor positioned local to said interface apparatus andseparate from said host computer system for receiving said host commandfrom said host computer system and providing a processor output controlsignal in accordance with said at least one command parameter; anactuator for receiving said processor output control signal andproviding a force along a degree of freedom to said user manipulableobject in accordance with said processor output control signal, saidobject being coupled to said actuator and being graspable and movable bysaid user; and a sensor for detecting motion of said manipulable objectalong said degree of freedom and outputting said input control signalincluding information representative of the position and motion of saidobject.
 2. A system as recited in claim 1 wherein said sensor outputssaid input control signal to said processor, and wherein said processorprovides said input control signal to said host computer system.
 3. Asystem as recited in claim 2 wherein said processor implements one of aplurality of reflex processes selected in accordance with said hostcommand and said command parameters to provide said processor outputcontrol signal to said actuator in response to said position and motionof said object independently of said host command.
 4. A system asrecited in claim 3 wherein a magnitude of said force output by saidactuator is determined by a force value output in said processor outputcontrol signal, said force value being determined by said selectedreflex process based on said at least one command parameter included insaid host command.
 5. A system as recited in claim 4 wherein a directionalong said degree of freedom of said force output by said actuator isdetermined by an indication of a direction in said processor outputcontrol signal, said direction being determined by said selected reflexprocess according to said at least one command parameter included insaid host command.
 6. A system as recited in claim 5 wherein said atleast one command parameter includes a magnitude parameter determining amagnitude of said force to be output by said actuator.
 7. A system asrecited in claim 5 wherein said at least one command parameter includesa duration parameter determining how long said force output by saidactuator is in effect.
 8. A system as recited in claim 5 wherein said atleast one command parameter includes a direction parameter determiningthe direction and degrees of freedom of said force output by saidactuator.
 9. A system as recited in claim 5 wherein said at least onecommand parameter includes button parameters which designate a buttoncoupled to said processor and determine a magnitude, direction, andduration of a force output by said actuators when said button is pressedby said user.
 10. A system as recited in claim 4 wherein said hostcomputer system displays images on a visual output device andmanipulates said images in accordance with a position and a motion ofsaid object.
 11. A system as recited in claim 10 wherein said displayedimages include a computer object in a computer environment directlymapped to a position of said user object, and wherein said host commandis a position control command operative to cause forces to be outputdirectly in accordance with the location of said computer object andsaid user object.
 12. A system as recited in claim 10 wherein saiddisplayed images include a computer object in a computer environment,wherein a motion of said computer object is directly mapped to aposition of said user object, and wherein said host command is a ratecontrol command operative to cause forces to be output directly inaccordance with a position of said user object in said degree of freedomand in accordance with a computer environment of said computer object.13. A system as recited in claim 10 wherein said displayed imagesinclude a computer object in a computer environment under control ofsaid user, and wherein said displayed images include a computer objectunder control of said user, and wherein said host command provides localposition control to cause output forces to be output in accordance witha location of said computer object and said user object, and providesglobal rate control to cause output forces to be output in accordancewith said computer environment and said user object.
 14. A system asrecited in claim 1 wherein said host computer and said processor arecoupled together by a serial interface.
 15. A system as recited in claim14 wherein said serial interface includes a Universal Serial Businterface.
 16. A system as recited in claim 3 wherein saidmicroprocessor and said actuator are including in a single housing andare coupled to said host computer by a communication interface.
 17. Amethod for interfacing a force feedback interface device manipulated bya user with a host computer system, the method comprising the steps of:providing a user manipulable object included in said force feedbackinterface device, said object having a degree of freedom; sensingpositions of said object along said degree of freedom with a sensor andproducing electrical sensor signals therefrom; utilizing amicroprocessor local to said object to communicate with said hostcomputer system to provide said electrical sensor signals to said hostcomputer system and to receive a host command from said host computersystem, said host command including a command parameter; and creating aforce on said object along said degree of freedom independentlyutilizing said microprocessor and said host command to control anactuator coupled to said object.
 18. A method as recited in claim 17wherein said step of creating a force on said user manipulable objectincludes the steps of: selecting a reflex process by said microprocessorin accordance with said host command; outputting processor forcecommands from said microprocessor to said actuator utilizing said reflexprocess and said electrical sensor signals.
 19. A method as recited inclaim 18 wherein said command parameter is a magnitude parameter forcontrolling a magnitude of said force output by said actuator.
 20. Amethod as recited in claim 19 wherein said command parameter is aduration parameter for controlling the time duration of said forceapplied to said user manipulable object.